diff --git a/packages/crm-service/src/contacts/contacts.service.ts b/packages/crm-service/src/contacts/contacts.service.ts
index 95712bd..a947c7d 100644
--- a/packages/crm-service/src/contacts/contacts.service.ts
+++ b/packages/crm-service/src/contacts/contacts.service.ts
@@ -52,6 +52,10 @@ export class ContactsService {
       where.type = query.type;
     }
 
+    if (query.companyId) {
+      where.companyId = query.companyId;
+    }
+
     if (query.search) {
       where.OR = [
         { firstName: { contains: query.search, mode: 'insensitive' } },
diff --git a/packages/crm-service/src/contacts/dto/query-contacts.dto.ts b/packages/crm-service/src/contacts/dto/query-contacts.dto.ts
index 9c045b4..b5c494c 100644
--- a/packages/crm-service/src/contacts/dto/query-contacts.dto.ts
+++ b/packages/crm-service/src/contacts/dto/query-contacts.dto.ts
@@ -1,4 +1,4 @@
-import { IsString, IsOptional, IsEnum } from 'class-validator';
+import { IsString, IsOptional, IsEnum, IsUUID } from 'class-validator';
 import { ApiPropertyOptional } from '@nestjs/swagger';
 import { PaginationDto } from '../../common/dto/pagination.dto';
 import { ContactType } from './create-contact.dto';
@@ -9,6 +9,11 @@ export class QueryContactsDto extends PaginationDto {
   @IsString()
   search?: string;
 
+  @ApiPropertyOptional({ description: 'Filter nach Unternehmen (UUID)' })
+  @IsOptional()
+  @IsUUID()
+  companyId?: string;
+
   @ApiPropertyOptional({ enum: ContactType })
   @IsOptional()
   @IsEnum(ContactType)
diff --git a/packages/frontend/src/crm/companies/CompaniesPage.module.css b/packages/frontend/src/crm/companies/CompaniesPage.module.css
index e18f0be..2a3a70e 100644
--- a/packages/frontend/src/crm/companies/CompaniesPage.module.css
+++ b/packages/frontend/src/crm/companies/CompaniesPage.module.css
@@ -54,3 +54,105 @@
   opacity: 0.4;
   cursor: not-allowed;
 }
+
+/* ============================================================
+   Expandable Rows — Kontakte als Sub-Rows
+   ============================================================ */
+
+/* Expand/Collapse Button */
+.expandBtn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 24px;
+  height: 24px;
+  padding: 0;
+  border: none;
+  border-radius: var(--radius-sm);
+  background: transparent;
+  cursor: pointer;
+  color: var(--color-text-muted);
+  transition: background 0.15s, color 0.15s;
+}
+
+.expandBtn:hover {
+  background: var(--color-bg);
+  color: var(--color-text);
+}
+
+.expandIcon {
+  display: inline-block;
+  font-size: 0.625rem;
+  transition: transform 0.2s ease;
+  line-height: 1;
+}
+
+/* Company row when expanded */
+.expandedRow {
+  background: var(--color-bg);
+}
+
+/* Contact sub-rows */
+.subRow {
+  background: var(--color-bg);
+  border-bottom: 1px solid var(--color-border);
+  cursor: pointer;
+}
+
+.subRow:hover {
+  background: var(--color-bg-card);
+}
+
+.subRowIndent {
+  padding: 0.5rem 0.5rem 0.5rem 1rem;
+  width: 40px;
+  position: relative;
+}
+
+.subRowConnector {
+  display: block;
+  width: 12px;
+  height: 1px;
+  background: var(--color-border);
+  margin-left: auto;
+}
+
+.subRowCell {
+  padding: 0.5rem 1rem;
+  font-size: 0.8125rem;
+  color: var(--color-text-secondary);
+}
+
+.subRowLoading,
+.subRowError,
+.subRowEmpty {
+  padding: 0.75rem 1rem 0.75rem 3.5rem;
+  font-size: 0.8125rem;
+  color: var(--color-text-muted);
+  font-style: italic;
+  text-align: left;
+}
+
+.subRowError {
+  color: var(--color-error);
+}
+
+/* Typ-Badge in Sub-Rows */
+.typeBadge {
+  display: inline-block;
+  padding: 0.0625rem 0.5rem;
+  border-radius: 9999px;
+  font-size: 0.6875rem;
+  font-weight: 600;
+  white-space: nowrap;
+}
+
+.typeBadge[data-type='PERSON'] {
+  background: #dbeafe;
+  color: #1e40af;
+}
+
+.typeBadge[data-type='ORGANIZATION'] {
+  background: #d1fae5;
+  color: #065f46;
+}
diff --git a/packages/frontend/src/crm/companies/CompaniesPage.tsx b/packages/frontend/src/crm/companies/CompaniesPage.tsx
index 47dbcea..912ba68 100644
--- a/packages/frontend/src/crm/companies/CompaniesPage.tsx
+++ b/packages/frontend/src/crm/companies/CompaniesPage.tsx
@@ -1,9 +1,9 @@
-import { useState, useEffect } from 'react';
+import { useState, useEffect, Fragment } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { Modal } from '../../components/Modal';
-import { useCompanies, useDeleteCompany } from '../hooks';
+import { useCompanies, useDeleteCompany, useCompanyContacts } from '../hooks';
 import { CompanyFormModal } from './CompanyFormModal';
-import type { Company, CompaniesQueryParams } from '../types';
+import type { Company, Contact, CompaniesQueryParams, ContactType } from '../types';
 import styles from './CompaniesPage.module.css';
 
 const thStyle: React.CSSProperties = {
@@ -14,6 +14,124 @@ const thStyle: React.CSSProperties = {
   color: 'var(--color-text-muted)',
 };
 
+const tdStyle: React.CSSProperties = {
+  padding: '0.75rem 1rem',
+  fontSize: '0.875rem',
+  color: 'var(--color-text-secondary)',
+};
+
+// --------------------------------------------------------
+// Kontakt-Anzeigename
+// --------------------------------------------------------
+function contactDisplayName(c: Contact): string {
+  if (c.type === 'ORGANIZATION') return c.companyName ?? '—';
+  return [c.firstName, c.lastName].filter(Boolean).join(' ') || '—';
+}
+
+const TYPE_LABELS: Record<ContactType, string> = {
+  PERSON: 'Person',
+  ORGANIZATION: 'Organisation',
+};
+
+// --------------------------------------------------------
+// ContactSubRows — lazy-loaded Kontakte eines Unternehmens
+// --------------------------------------------------------
+function ContactSubRows({ companyId }: { companyId: string }) {
+  const navigate = useNavigate();
+  const { data, isLoading, error } = useCompanyContacts(companyId, true);
+
+  if (isLoading) {
+    return (
+      <tr className={styles.subRow}>
+        <td colSpan={9} className={styles.subRowLoading}>
+          Kontakte laden...
+        </td>
+      </tr>
+    );
+  }
+
+  if (error) {
+    return (
+      <tr className={styles.subRow}>
+        <td colSpan={9} className={styles.subRowError}>
+          Fehler beim Laden der Kontakte
+        </td>
+      </tr>
+    );
+  }
+
+  const contacts = data?.data ?? [];
+
+  if (contacts.length === 0) {
+    return (
+      <tr className={styles.subRow}>
+        <td colSpan={9} className={styles.subRowEmpty}>
+          Keine Kontakte vorhanden
+        </td>
+      </tr>
+    );
+  }
+
+  return (
+    <>
+      {contacts.map((contact) => (
+        <tr
+          key={contact.id}
+          className={styles.subRow}
+          onClick={() => navigate(`/crm/contacts/${contact.id}`)}
+        >
+          {/* Indent / Connector */}
+          <td className={styles.subRowIndent}>
+            <span className={styles.subRowConnector} />
+          </td>
+          {/* Name */}
+          <td className={styles.subRowCell} style={{ fontWeight: 500 }}>
+            {contactDisplayName(contact)}
+          </td>
+          {/* Position (anstelle Branche) */}
+          <td className={styles.subRowCell}>
+            {contact.position ?? '—'}
+          </td>
+          {/* E-Mail */}
+          <td className={styles.subRowCell}>
+            {contact.email ?? '—'}
+          </td>
+          {/* Telefon (anstelle Kontakte-Zahl) */}
+          <td className={styles.subRowCell}>
+            {contact.phone ?? contact.mobile ?? '—'}
+          </td>
+          {/* Typ-Badge (anstelle Vorgaenge) */}
+          <td className={styles.subRowCell} style={{ textAlign: 'center' }}>
+            <span className={styles.typeBadge} data-type={contact.type}>
+              {TYPE_LABELS[contact.type] ?? '—'}
+            </span>
+          </td>
+          {/* Status */}
+          <td className={styles.subRowCell}>
+            <span
+              style={{
+                display: 'inline-block',
+                width: 8,
+                height: 8,
+                borderRadius: '50%',
+                background: contact.isActive
+                  ? 'var(--color-success)'
+                  : 'var(--color-error)',
+              }}
+              title={contact.isActive ? 'Aktiv' : 'Inaktiv'}
+            />
+          </td>
+          {/* Leere Aktionen-Spalte */}
+          <td className={styles.subRowCell} />
+        </tr>
+      ))}
+    </>
+  );
+}
+
+// --------------------------------------------------------
+// CompaniesPage — Hauptkomponente
+// --------------------------------------------------------
 export function CompaniesPage() {
   const navigate = useNavigate();
   const [page, setPage] = useState(1);
@@ -22,6 +140,7 @@ export function CompaniesPage() {
   const [isCreateOpen, setCreateOpen] = useState(false);
   const [editingCompany, setEditingCompany] = useState<Company | null>(null);
   const [deletingCompany, setDeletingCompany] = useState<Company | null>(null);
+  const [expandedIds, setExpandedIds] = useState<Set<string>>(new Set());
 
   // Debounced search
   useEffect(() => {
@@ -32,6 +151,11 @@ export function CompaniesPage() {
     return () => clearTimeout(t);
   }, [searchInput]);
 
+  // Reset expanded rows on page change
+  useEffect(() => {
+    setExpandedIds(new Set());
+  }, [page]);
+
   const params: CompaniesQueryParams = {
     page,
     pageSize: 25,
@@ -43,6 +167,19 @@ export function CompaniesPage() {
   const { data, isLoading, error } = useCompanies(params);
   const deleteMutation = useDeleteCompany();
 
+  const toggleExpand = (companyId: string, e: React.MouseEvent) => {
+    e.stopPropagation();
+    setExpandedIds((prev) => {
+      const next = new Set(prev);
+      if (next.has(companyId)) {
+        next.delete(companyId);
+      } else {
+        next.add(companyId);
+      }
+      return next;
+    });
+  };
+
   if (isLoading) return <p>Laden...</p>;
   if (error)
     return (
@@ -122,9 +259,9 @@ export function CompaniesPage() {
                 background: 'var(--color-bg)',
               }}
             >
+              <th style={{ ...thStyle, width: '40px', padding: '0.75rem 0.5rem' }} />
               <th style={thStyle}>Name</th>
               <th style={thStyle}>Branche</th>
-              <th style={thStyle}>Stadt</th>
               <th style={thStyle}>E-Mail</th>
               <th style={{ ...thStyle, textAlign: 'center' }}>Kontakte</th>
               <th style={{ ...thStyle, textAlign: 'center' }}>Vorgänge</th>
@@ -136,7 +273,7 @@ export function CompaniesPage() {
             {companies.length === 0 && (
               <tr>
                 <td
-                  colSpan={8}
+                  colSpan={9}
                   style={{
                     padding: '2rem',
                     textAlign: 'center',
@@ -147,122 +284,127 @@ export function CompaniesPage() {
                 </td>
               </tr>
             )}
-            {companies.map((company) => (
-              <tr
-                key={company.id}
-                style={{
-                  borderBottom: '1px solid var(--color-border)',
-                  cursor: 'pointer',
-                }}
-                onClick={() => navigate(`/crm/companies/${company.id}`)}
-              >
-                <td
-                  style={{
-                    padding: '0.75rem 1rem',
-                    fontSize: '0.875rem',
-                    fontWeight: 500,
-                  }}
-                >
-                  {company.name}
-                </td>
-                <td
-                  style={{
-                    padding: '0.75rem 1rem',
-                    fontSize: '0.875rem',
-                    color: 'var(--color-text-secondary)',
-                  }}
-                >
-                  {company.industry ?? '—'}
-                </td>
-                <td
-                  style={{
-                    padding: '0.75rem 1rem',
-                    fontSize: '0.875rem',
-                    color: 'var(--color-text-secondary)',
-                  }}
-                >
-                  {company.city ?? '—'}
-                </td>
-                <td
-                  style={{
-                    padding: '0.75rem 1rem',
-                    fontSize: '0.875rem',
-                    color: 'var(--color-text-secondary)',
-                  }}
-                >
-                  {company.email ?? '—'}
-                </td>
-                <td
-                  style={{
-                    padding: '0.75rem 1rem',
-                    fontSize: '0.875rem',
-                    textAlign: 'center',
-                    color: 'var(--color-text-secondary)',
-                  }}
-                >
-                  {company._count?.contacts ?? 0}
-                </td>
-                <td
-                  style={{
-                    padding: '0.75rem 1rem',
-                    fontSize: '0.875rem',
-                    textAlign: 'center',
-                    color: 'var(--color-text-secondary)',
-                  }}
-                >
-                  {company._count?.deals ?? 0}
-                </td>
-                <td style={{ padding: '0.75rem 1rem' }}>
-                  <span
+            {companies.map((company) => {
+              const contactCount = company._count?.contacts ?? 0;
+              const isExpanded = expandedIds.has(company.id);
+
+              return (
+                <Fragment key={company.id}>
+                  {/* Company Row */}
+                  <tr
+                    className={isExpanded ? styles.expandedRow : undefined}
                     style={{
-                      display: 'inline-block',
-                      width: 8,
-                      height: 8,
-                      borderRadius: '50%',
-                      background: company.isActive
-                        ? 'var(--color-success)'
-                        : 'var(--color-error)',
+                      borderBottom: '1px solid var(--color-border)',
+                      cursor: 'pointer',
                     }}
-                    title={company.isActive ? 'Aktiv' : 'Inaktiv'}
-                  />
-                </td>
-                <td
-                  style={{ padding: '0.75rem 1rem' }}
-                  onClick={(e) => e.stopPropagation()}
-                >
-                  <div style={{ display: 'flex', gap: '0.5rem' }}>
-                    <button
-                      onClick={() => setEditingCompany(company)}
+                    onClick={() => navigate(`/crm/companies/${company.id}`)}
+                  >
+                    {/* Expand Button */}
+                    <td
+                      style={{ padding: '0.75rem 0.5rem', textAlign: 'center', width: '40px' }}
+                      onClick={(e) => contactCount > 0 && toggleExpand(company.id, e)}
+                    >
+                      {contactCount > 0 && (
+                        <button
+                          className={styles.expandBtn}
+                          aria-expanded={isExpanded}
+                          aria-label={isExpanded ? 'Kontakte einklappen' : 'Kontakte aufklappen'}
+                        >
+                          <span
+                            className={styles.expandIcon}
+                            style={{
+                              transform: isExpanded ? 'rotate(90deg)' : 'rotate(0deg)',
+                            }}
+                          >
+                            &#9654;
+                          </span>
+                        </button>
+                      )}
+                    </td>
+                    {/* Name */}
+                    <td
                       style={{
-                        padding: '0.25rem 0.625rem',
-                        fontSize: '0.8125rem',
-                        background: 'transparent',
-                        border: '1px solid var(--color-border)',
-                        borderRadius: 'var(--radius-sm)',
-                        cursor: 'pointer',
-                        color: 'var(--color-text-secondary)',
+                        padding: '0.75rem 1rem',
+                        fontSize: '0.875rem',
+                        fontWeight: 500,
                       }}
                     >
-                      Bearbeiten
-                    </button>
-                    <button
-                      onClick={() => setDeletingCompany(company)}
-                      style={{
-                        padding: '0.25rem 0.625rem',
-                        fontSize: '0.8125rem',
-                        background: 'transparent',
-                        border: '1px solid #fecaca',
-                        borderRadius: 'var(--radius-sm)',
-                        cursor: 'pointer',
-                        color: 'var(--color-error)',
-                      }}
+                      {company.name}
+                    </td>
+                    {/* Branche */}
+                    <td style={tdStyle}>
+                      {company.industry ?? '—'}
+                    </td>
+                    {/* E-Mail */}
+                    <td style={tdStyle}>
+                      {company.email ?? '—'}
+                    </td>
+                    {/* Kontakte */}
+                    <td style={{ ...tdStyle, textAlign: 'center' }}>
+                      {contactCount}
+                    </td>
+                    {/* Vorgaenge */}
+                    <td style={{ ...tdStyle, textAlign: 'center' }}>
+                      {company._count?.deals ?? 0}
+                    </td>
+                    {/* Status */}
+                    <td style={{ padding: '0.75rem 1rem' }}>
+                      <span
+                        style={{
+                          display: 'inline-block',
+                          width: 8,
+                          height: 8,
+                          borderRadius: '50%',
+                          background: company.isActive
+                            ? 'var(--color-success)'
+                            : 'var(--color-error)',
+                        }}
+                        title={company.isActive ? 'Aktiv' : 'Inaktiv'}
+                      />
+                    </td>
+                    {/* Aktionen */}
+                    <td
+                      style={{ padding: '0.75rem 1rem' }}
+                      onClick={(e) => e.stopPropagation()}
                     >
-                      Löschen
-                    </button>
-                  </div>
-                </td>
-              </tr>
-            ))}
+                      <div style={{ display: 'flex', gap: '0.5rem' }}>
+                        <button
+                          onClick={() => setEditingCompany(company)}
+                          style={{
+                            padding: '0.25rem 0.625rem',
+                            fontSize: '0.8125rem',
+                            background: 'transparent',
+                            border: '1px solid var(--color-border)',
+                            borderRadius: 'var(--radius-sm)',
+                            cursor: 'pointer',
+                            color: 'var(--color-text-secondary)',
+                          }}
+                        >
+                          Bearbeiten
+                        </button>
+                        <button
+                          onClick={() => setDeletingCompany(company)}
+                          style={{
+                            padding: '0.25rem 0.625rem',
+                            fontSize: '0.8125rem',
+                            background: 'transparent',
+                            border: '1px solid #fecaca',
+                            borderRadius: 'var(--radius-sm)',
+                            cursor: 'pointer',
+                            color: 'var(--color-error)',
+                          }}
+                        >
+                          Löschen
+                        </button>
+                      </div>
+                    </td>
+                  </tr>
+
+                  {/* Contact Sub-Rows (lazy-loaded) */}
+                  {isExpanded && <ContactSubRows companyId={company.id} />}
+                </Fragment>
+              );
+            })}
           </tbody>
         </table>
 
diff --git a/packages/frontend/src/crm/hooks.ts b/packages/frontend/src/crm/hooks.ts
index a9abd53..c4fccbe 100644
--- a/packages/frontend/src/crm/hooks.ts
+++ b/packages/frontend/src/crm/hooks.ts
@@ -53,6 +53,8 @@ export const crmKeys = {
     list: (params: ContactsQueryParams) =>
       ['crm', 'contacts', 'list', params] as const,
     detail: (id: string) => ['crm', 'contacts', 'detail', id] as const,
+    byCompany: (companyId: string) =>
+      ['crm', 'contacts', 'byCompany', companyId] as const,
   },
   deals: {
     all: ['crm', 'deals'] as const,
@@ -166,6 +168,25 @@ export function useDeleteContact() {
   });
 }
 
+/**
+ * Lazy-load contacts for a specific company (expandable rows).
+ * Only fetches when enabled is true (i.e., the row is expanded).
+ */
+export function useCompanyContacts(companyId: string, enabled: boolean) {
+  return useQuery({
+    queryKey: crmKeys.contacts.byCompany(companyId),
+    queryFn: () =>
+      contactsApi.list({
+        companyId,
+        pageSize: 50,
+        sort: 'lastName',
+        order: 'asc',
+      }),
+    enabled: enabled && !!companyId,
+    staleTime: 2 * 60 * 1000,
+  });
+}
+
 // ============================================================
 //  Deals
 // ============================================================
diff --git a/packages/frontend/src/crm/types.ts b/packages/frontend/src/crm/types.ts
index 4ed4ac0..cb05ea3 100644
--- a/packages/frontend/src/crm/types.ts
+++ b/packages/frontend/src/crm/types.ts
@@ -412,6 +412,7 @@ export interface ContactsQueryParams {
   pageSize?: number;
   search?: string;
   type?: ContactType;
+  companyId?: string;
   sort?: string;
   order?: 'asc' | 'desc';
 }