diff --git a/src/caching/cache-key.builder.ts b/src/caching/cache-key.builder.ts
index 715a2f20..fa8919ed 100644
--- a/src/caching/cache-key.builder.ts
+++ b/src/caching/cache-key.builder.ts
@@ -2,46 +2,63 @@ import { CACHE_PREFIXES } from './caching.constants';
 import { SearchFilters } from '../search/search.service';
 import { SEARCH_CONSTANTS } from '../search/search.constants';
 
-export function buildCourseListKey(scope: 'published' | 'all' = 'published'): string {
-  return `${CACHE_PREFIXES.COURSES_LIST}:${scope}`;
+function assertTenantId(tenantId: string | undefined, context: string): string {
+  if (typeof tenantId !== 'string' || tenantId.trim().length === 0) {
+    throw new Error(`Tenant identifier is required for ${context}`);
+  }
+  return tenantId;
+}
+
+export function buildCourseListKey(
+  tenantId: string,
+  scope: 'published' | 'all' = 'published',
+): string {
+  const resolvedTenantId = assertTenantId(tenantId, 'course list cache key');
+  return `cache:${resolvedTenantId}:${CACHE_PREFIXES.COURSES_LIST.replace('cache:', '')}:${scope}`;
 }
 
-export function buildPopularCoursesKey(): string {
-  return `${CACHE_PREFIXES.POPULAR}:courses`;
+export function buildPopularCoursesKey(tenantId: string): string {
+  const resolvedTenantId = assertTenantId(tenantId, 'popular courses cache key');
+  return `cache:${resolvedTenantId}:${CACHE_PREFIXES.POPULAR.replace('cache:', '')}:courses`;
 }
 
-export function buildCourseKey(courseId: string): string {
-  return `${CACHE_PREFIXES.COURSE}:${courseId}`;
+export function buildCourseKey(tenantId: string, courseId: string): string {
+  const resolvedTenantId = assertTenantId(tenantId, 'course cache key');
+  return `cache:${resolvedTenantId}:${CACHE_PREFIXES.COURSE.replace('cache:', '')}:${courseId}`;
 }
 
-export function buildUserProfileKey(userId: string): string {
-  return `${CACHE_PREFIXES.USER_PROFILE}:${userId}`;
+export function buildUserProfileKey(tenantId: string, userId: string): string {
+  const resolvedTenantId = assertTenantId(tenantId, 'user profile cache key');
+  return `cache:${resolvedTenantId}:${CACHE_PREFIXES.USER_PROFILE.replace('cache:', '')}:${userId}`;
 }
 
 export function buildSearchCacheKey(
+  tenantId: string,
   query: string,
   filters?: SearchFilters,
   sort?: string,
   page = 1,
   limit: number = SEARCH_CONSTANTS.DEFAULT_PAGE_SIZE,
 ): string {
+  const resolvedTenantId = assertTenantId(tenantId, 'search cache key');
   const str = `${query}:${JSON.stringify(filters ?? {})}:${sort ?? 'default'}:${page}:${limit}`;
   let hash = 0;
   for (let i = 0; i < str.length; i++) {
     hash = (hash << 5) - hash + str.charCodeAt(i);
     hash = hash & hash;
   }
-  return `${CACHE_PREFIXES.SEARCH}:${hash.toString()}`;
+  return `cache:${resolvedTenantId}:${CACHE_PREFIXES.SEARCH.replace('cache:', '')}:${hash.toString()}`;
 }
 
 // ---------------------------------------------------------------------------
 // Computation cache key builder — Issue #603
 //
-// Format: cache:computation:<type>:<identifier>
+// Format: cache:{tenant}:computation:{type}:{identifier}
 // Examples:
-//   cache:computation:leaderboard:top-players:10
-//   cache:computation:leaderboard:user-rank:user-abc
+//   cache:tenant-a:computation:leaderboard:top-players:10
+//   cache:tenant-a:computation:leaderboard:user-rank:user-abc
 // ---------------------------------------------------------------------------
-export function buildComputationKey(type: string, identifier: string): string {
-  return `cache:computation:${type}:${identifier}`;
+export function buildComputationKey(tenantId: string, type: string, identifier: string): string {
+  const resolvedTenantId = assertTenantId(tenantId, 'computation cache key');
+  return `cache:${resolvedTenantId}:computation:${type}:${identifier}`;
 }
diff --git a/src/caching/cache-warming.service.spec.ts b/src/caching/cache-warming.service.spec.ts
index 9bff0793..b03a85e3 100644
--- a/src/caching/cache-warming.service.spec.ts
+++ b/src/caching/cache-warming.service.spec.ts
@@ -5,6 +5,7 @@ import { Enrollment } from '../courses/entities/enrollment.entity';
 import { User } from '../users/entities/user.entity';
 import { ProfileCompletenessService } from '../profile-completeness/profile-completeness.service';
 import { SearchService } from '../search/search.service';
+import { IsolationService } from '../tenancy/isolation/isolation.service';
 import { CachingService } from './caching.service';
 import { CacheWarmingService } from './cache-warming.service';
 import { CACHE_TTL } from './caching.constants';
@@ -25,7 +26,10 @@ describe('CacheWarmingService', () => {
   let profileCompleteness: { getScore: jest.Mock };
 
   beforeEach(async () => {
-    caching = { set: jest.fn().mockResolvedValue(undefined) };
+    caching = {
+      set: jest.fn().mockResolvedValue(undefined),
+      getCurrentTenantId: jest.fn().mockReturnValue('tenant-a'),
+    } as any;
     courseRepo = { find: jest.fn() };
     enrollmentRepo = { createQueryBuilder: jest.fn() };
     userRepo = { find: jest.fn() };
@@ -40,8 +44,12 @@ describe('CacheWarmingService', () => {
       providers: [
         CacheWarmingService,
         { provide: CachingService, useValue: caching },
+        {
+          provide: ProfileCompletenessService,
+          useValue: profileCompleteness,
+        },
         { provide: SearchService, useValue: searchService },
-        { provide: ProfileCompletenessService, useValue: profileCompleteness },
+        { provide: IsolationService, useValue: { getTenantId: jest.fn().mockReturnValue('tenant-a') } },
         { provide: getRepositoryToken(Course), useValue: courseRepo },
         { provide: getRepositoryToken(Enrollment), useValue: enrollmentRepo },
         { provide: getRepositoryToken(User), useValue: userRepo },
@@ -59,7 +67,7 @@ describe('CacheWarmingService', () => {
 
     expect(result.target).toBe('COURSES_LIST');
     expect(caching.set).toHaveBeenCalledWith(
-      buildCourseListKey('published'),
+      buildCourseListKey('tenant-a', 'published'),
       courses,
       CACHE_TTL.COURSE_METADATA,
     );
@@ -82,7 +90,7 @@ describe('CacheWarmingService', () => {
 
     expect(result.target).toBe('POPULAR_COURSES');
     expect(caching.set).toHaveBeenCalledWith(
-      buildPopularCoursesKey(),
+      buildPopularCoursesKey('tenant-a'),
       [{ id: 'c1' }],
       CACHE_TTL.POPULAR_COURSES,
     );
@@ -95,7 +103,7 @@ describe('CacheWarmingService', () => {
     expect(result.keysWarmed).toBeGreaterThan(0);
     expect(searchService.search).toHaveBeenCalled();
     expect(caching.set).toHaveBeenCalledWith(
-      buildSearchCacheKey(''),
+      buildSearchCacheKey('tenant-a', ''),
       expect.any(Object),
       CACHE_TTL.SEARCH_RESULTS,
     );
@@ -109,7 +117,7 @@ describe('CacheWarmingService', () => {
     expect(result.target).toBe('USER_PROFILE');
     expect(profileCompleteness.getScore).toHaveBeenCalledWith('u1');
     expect(caching.set).toHaveBeenCalledWith(
-      buildUserProfileKey('u1'),
+      buildUserProfileKey('tenant-a', 'u1'),
       expect.objectContaining({ score: 80 }),
       CACHE_TTL.USER_PROFILE,
     );
diff --git a/src/caching/cache-warming.service.ts b/src/caching/cache-warming.service.ts
index 8f8fcf04..4bf1d3cb 100644
--- a/src/caching/cache-warming.service.ts
+++ b/src/caching/cache-warming.service.ts
@@ -8,6 +8,7 @@ import { ProfileCompletenessService } from '../profile-completeness/profile-comp
 import { SearchService } from '../search/search.service';
 import { CachingService } from './caching.service';
 import { CACHE_TTL, CACHE_WARMING } from './caching.constants';
+import { IsolationService } from '../tenancy/isolation/isolation.service';
 import {
   buildCourseListKey,
   buildPopularCoursesKey,
@@ -30,6 +31,7 @@ export class CacheWarmingService {
 
   constructor(
     private readonly caching: CachingService,
+    private readonly isolationService: IsolationService,
     private readonly searchService: SearchService,
     private readonly profileCompleteness: ProfileCompletenessService,
     @InjectRepository(Course)
@@ -51,7 +53,11 @@ export class CacheWarmingService {
 
   async warmCoursesList(): Promise<WarmResult> {
     const started = Date.now();
-    const key = buildCourseListKey('published');
+    const tenantId = this.caching.getCurrentTenantId();
+    if (!tenantId) {
+      throw new Error('Tenant context is required for tenant-scoped cache warmup');
+    }
+    const key = buildCourseListKey(tenantId, 'published');
     const courses = await this.courseRepo.find({
       where: { status: CourseStatus.PUBLISHED },
       order: { createdAt: 'DESC' },
@@ -67,7 +73,11 @@ export class CacheWarmingService {
 
   async warmPopularCourses(): Promise<WarmResult> {
     const started = Date.now();
-    const key = buildPopularCoursesKey();
+    const tenantId = this.isolationService.getTenantId();
+    if (!tenantId) {
+      throw new Error('Tenant context is required for tenant-scoped cache warmup');
+    }
+    const key = buildPopularCoursesKey(tenantId);
     const popular = await this.enrollmentRepo
       .createQueryBuilder('enrollment')
       .select('enrollment.courseId', 'courseId')
@@ -107,14 +117,19 @@ export class CacheWarmingService {
     const started = Date.now();
     let keysWarmed = 0;
 
+    const tenantId = this.isolationService.getTenantId();
+    if (!tenantId) {
+      throw new Error('Tenant context is required for tenant-scoped cache warmup');
+    }
+
     for (const query of CACHE_WARMING.SEARCH_WARM_QUERIES) {
       const result = await this.searchService.search(query);
-      const key = buildSearchCacheKey(query);
+      const key = buildSearchCacheKey(tenantId, query);
       await this.caching.set(key, result, CACHE_TTL.SEARCH_RESULTS);
       keysWarmed += 1;
     }
 
-    const filtersKey = buildSearchCacheKey('', { level: 'beginner' });
+    const filtersKey = buildSearchCacheKey(tenantId, '', { level: 'beginner' });
     const filteredResult = await this.searchService.search('', { level: 'beginner' });
     await this.caching.set(filtersKey, filteredResult, CACHE_TTL.SEARCH_RESULTS);
     keysWarmed += 1;
@@ -142,10 +157,15 @@ export class CacheWarmingService {
       });
     }
 
+    const tenantId = this.isolationService.getTenantId();
+    if (!tenantId) {
+      throw new Error('Tenant context is required for tenant-scoped cache warmup');
+    }
+
     await Promise.all(
       users.map(async (user) => {
         const profile = await this.profileCompleteness.getScore(user.id);
-        const key = buildUserProfileKey(user.id);
+        const key = buildUserProfileKey(tenantId, user.id);
         await this.caching.set(key, profile, CACHE_TTL.USER_PROFILE);
       }),
     );
diff --git a/src/caching/caching.module.ts b/src/caching/caching.module.ts
index 76d798b6..6ea4d085 100644
--- a/src/caching/caching.module.ts
+++ b/src/caching/caching.module.ts
@@ -29,6 +29,7 @@ import { QueryCacheService } from './query-cache.service';
     EventEmitterModule.forRoot(),
     MonitoringModule,
     SearchModule,
+    TenancyModule,
     TypeOrmModule.forFeature([Course, Enrollment, User]),
     CacheModule.registerAsync({
       imports: [ConfigModule],
diff --git a/src/caching/caching.service.spec.ts b/src/caching/caching.service.spec.ts
index 74b74b75..91ac1c5e 100644
--- a/src/caching/caching.service.spec.ts
+++ b/src/caching/caching.service.spec.ts
@@ -72,10 +72,11 @@ describe('CachingService', () => {
   // ── deriveCacheType / buildCounterKeys ──────────────────────────────────────
 
   describe('deriveCacheType', () => {
-    it('returns the second segment for cache:{type}:... keys', () => {
+    it('returns the second segment for cache:{type}:... keys and the third for tenant-scoped keys', () => {
       expect(deriveCacheType('cache:test:1')).toBe('test');
       expect(deriveCacheType('cache:user:42')).toBe('user');
       expect(deriveCacheType('cache:course:popular')).toBe('course');
+      expect(deriveCacheType('cache:tenant-a:course:popular')).toBe('course');
     });
 
     it('returns "default" for keys with no cache: prefix', () => {
@@ -135,7 +136,7 @@ describe('CachingService', () => {
 
       expect(result).toEqual({ id: '2' });
       expect(factory).toHaveBeenCalledTimes(1);
-      expect(cacheManager.set).toHaveBeenCalledWith('cache:test:2', { id: '2' }, 120000);
+      expect(cacheManager.set).toHaveBeenCalledWith('cache:tenant-a:test:2', { id: '2' }, 120000);
       expect(redis.incr).toHaveBeenCalledWith('cache:misses:test');
 
       const stats = await service.getStats('test');
diff --git a/src/caching/caching.service.ts b/src/caching/caching.service.ts
index e3e26f6d..a6b0c507 100644
--- a/src/caching/caching.service.ts
+++ b/src/caching/caching.service.ts
@@ -41,6 +41,9 @@ export const deriveCacheType = (key: string): string => {
 
   const parts = key.split(':');
   if (parts.length >= 2 && parts[0] === 'cache') {
+    if (parts.length >= 4) {
+      return parts[2] || CACHE_TYPE_FALLBACK;
+    }
     return parts[1] || CACHE_TYPE_FALLBACK;
   }
   return CACHE_TYPE_FALLBACK;
@@ -138,19 +141,52 @@ export class CachingService {
     }
   }
 
-  async get<T>(key: string): Promise<T | undefined> {
-    const value = await this.cacheManager.get<T>(key);
+  getCurrentTenantId(): string | undefined {
+    return this.resolveTenantId();
+  }
+
+  private resolveTenantId(explicitTenantId?: string): string | undefined {
+    if (typeof explicitTenantId === 'string' && explicitTenantId.trim().length > 0) {
+      return explicitTenantId;
+    }
+
+    const tenantIdFromIsolation = this.isolationService?.getTenantId();
+    if (typeof tenantIdFromIsolation === 'string' && tenantIdFromIsolation.trim().length > 0) {
+      return tenantIdFromIsolation;
+    }
+
+    return undefined;
+  }
+
+  private buildTenantScopedKey(key: string, explicitTenantId?: string): string {
+    const tenantId = this.resolveTenantId(explicitTenantId);
+    if (!tenantId) {
+      throw new Error('Tenant context is required for tenant-scoped cache keys');
+    }
+
+    if (key.startsWith(`cache:${tenantId}:`)) {
+      return key;
+    }
+
+    const normalizedKey = key.startsWith('cache:') ? key.slice('cache:'.length) : key;
+    return `cache:${tenantId}:${normalizedKey}`;
+  }
+
+  async get<T>(key: string, tenantId?: string): Promise<T | undefined> {
+    const scopedKey = this.buildTenantScopedKey(key, tenantId);
+    const value = await this.cacheManager.get<T>(scopedKey);
     if (value === undefined || value === null) {
-      await this.recordMiss(deriveCacheType(key), key);
+      await this.recordMiss(deriveCacheType(scopedKey), scopedKey);
       return undefined;
     }
-    await this.recordHit(deriveCacheType(key), key);
+    await this.recordHit(deriveCacheType(scopedKey), scopedKey);
     return value;
   }
 
-  async set<T>(key: string, value: T, ttlSeconds?: number): Promise<void> {
+  async set<T>(key: string, value: T, ttlSeconds?: number, tenantId?: string): Promise<void> {
     const ttlMs = ttlSeconds !== undefined ? ttlSeconds * 1000 : undefined;
-    await this.cacheManager.set(key, value, ttlMs);
+    const scopedKey = this.buildTenantScopedKey(key, tenantId);
+    await this.cacheManager.set(scopedKey, value, ttlMs);
   }
 
   /**
@@ -214,16 +250,18 @@ export class CachingService {
     }
 
     const value = await factory();
-    await this.set(key, value, ttlSeconds);
+    await this.set(scopedKey, value, ttlSeconds, tenantId);
     return value;
   }
 
-  async delete(key: string): Promise<void> {
-    await this.cacheManager.del(key);
+  async delete(key: string, tenantId?: string): Promise<void> {
+    const scopedKey = this.buildTenantScopedKey(key, tenantId);
+    await this.cacheManager.del(scopedKey);
   }
 
-  async deleteMany(keys: string[]): Promise<void> {
-    await Promise.all(keys.map((key) => this.cacheManager.del(key)));
+  async deleteMany(keys: string[], tenantId?: string): Promise<void> {
+    const scopedKeys = keys.map((key) => this.buildTenantScopedKey(key, tenantId));
+    await Promise.all(scopedKeys.map((scopedKey) => this.cacheManager.del(scopedKey)));
   }
 
   async clear(): Promise<void> {
diff --git a/src/caching/computation-cache.service.spec.ts b/src/caching/computation-cache.service.spec.ts
index 5c5df0bc..26934cb7 100644
--- a/src/caching/computation-cache.service.spec.ts
+++ b/src/caching/computation-cache.service.spec.ts
@@ -1,6 +1,7 @@
 import { ComputationCacheService } from './computation-cache.service';
 import { CachingService } from './caching.service';
 import { MetricsCollectionService } from '../monitoring/metrics/metrics-collection.service';
+import { IsolationService } from '../tenancy/isolation/isolation.service';
 import { COMPUTATION_TTL } from './caching.constants';
 
 describe('ComputationCacheService', () => {
@@ -17,10 +18,12 @@ describe('ComputationCacheService', () => {
       get: jest.fn(),
       set: jest.fn().mockResolvedValue(undefined),
       delete: jest.fn().mockResolvedValue(undefined),
+      getCurrentTenantId: jest.fn().mockReturnValue('tenant-a'),
     };
     metrics = { updateCacheHitRate: jest.fn() };
     service = new ComputationCacheService(
       caching as unknown as CachingService,
+      { getTenantId: jest.fn().mockReturnValue('tenant-a') } as unknown as IsolationService,
       metrics as unknown as MetricsCollectionService,
     );
   });
diff --git a/src/caching/computation-cache.service.ts b/src/caching/computation-cache.service.ts
index 1c06c730..3f863b9b 100644
--- a/src/caching/computation-cache.service.ts
+++ b/src/caching/computation-cache.service.ts
@@ -2,6 +2,7 @@ import { Injectable, Logger, Optional } from '@nestjs/common';
 import { CachingService } from './caching.service';
 import { MetricsCollectionService } from '../monitoring/metrics/metrics-collection.service';
 import { buildComputationKey } from './cache-key.builder';
+import { IsolationService } from '../tenancy/isolation/isolation.service';
 
 export interface ComputationCacheStats {
   hits: number;
@@ -47,6 +48,7 @@ export class ComputationCacheService {
 
   constructor(
     private readonly caching: CachingService,
+    private readonly isolationService: IsolationService,
     @Optional() private readonly metrics?: MetricsCollectionService,
   ) {}
 
@@ -65,7 +67,11 @@ export class ComputationCacheService {
     factory: () => Promise<T>,
     ttlSeconds: number,
   ): Promise<T> {
-    const key = buildComputationKey(type, identifier);
+    const tenantId = this.isolationService.getTenantId();
+    if (!tenantId) {
+      throw new Error('Tenant context is required for tenant-scoped computation cache');
+    }
+    const key = buildComputationKey(tenantId, type, identifier);
 
     // ── Cache hit ──────────────────────────────────────────────────────────
     const cached = await this.caching.get<T>(key);
@@ -103,7 +109,11 @@ export class ComputationCacheService {
    * Invalidates a specific computation cache entry.
    */
   async invalidate(type: string, identifier: string): Promise<void> {
-    const key = buildComputationKey(type, identifier);
+    const tenantId = this.isolationService.getTenantId();
+    if (!tenantId) {
+      throw new Error('Tenant context is required for tenant-scoped computation cache');
+    }
+    const key = buildComputationKey(tenantId, type, identifier);
     await this.caching.delete(key);
     this.logger.debug(`Invalidated computation cache [${type}] key: ${key}`);
   }