diff --git a/src/lib/integrations/youtube/VideoMetricsSyncService.ts b/src/lib/integrations/youtube/VideoMetricsSyncService.ts
new file mode 100644
index 0000000..dcd7742
--- /dev/null
+++ b/src/lib/integrations/youtube/VideoMetricsSyncService.ts
@@ -0,0 +1,182 @@
+// src/lib/integrations/youtube/VideoMetricsSyncService.ts
+
+import type { Payload } from 'payload'
+
+import { YouTubeClient } from './YouTubeClient.js'
+
+const YOUTUBE_API_BATCH_LIMIT = 50
+
+interface MetricsSyncResult {
+  success: boolean
+  syncedCount: number
+  skippedCount: number
+  errors: string[]
+  syncedAt: Date
+}
+
+/**
+ * Syncs video performance metrics from YouTube API to YouTubeContent.performance fields.
+ *
+ * Fetches view counts, like counts, and comment counts for all published/tracked
+ * videos of a given channel and updates their performance fields in the database.
+ */
+export class VideoMetricsSyncService {
+  private payload: Payload
+
+  constructor(payload: Payload) {
+    this.payload = payload
+  }
+
+  /**
+   * Sync metrics for all published/tracked videos of a YouTube channel.
+   */
+  async syncMetrics(channelId: number): Promise<MetricsSyncResult> {
+    const result: MetricsSyncResult = {
+      success: false,
+      syncedCount: 0,
+      skippedCount: 0,
+      errors: [],
+      syncedAt: new Date(),
+    }
+
+    try {
+      // 1. Load the YouTube channel
+      const channel = await this.payload.findByID({
+        collection: 'youtube-channels',
+        id: channelId,
+      })
+
+      if (!channel) {
+        result.errors.push(`YouTube channel with ID ${channelId} not found`)
+        return result
+      }
+
+      // 2. Find the social account linked to this channel
+      const socialAccounts = await this.payload.find({
+        collection: 'social-accounts',
+        where: {
+          linkedChannel: { equals: channelId },
+          isActive: { equals: true },
+        },
+        limit: 1,
+      })
+
+      const account = socialAccounts.docs[0]
+      if (!account) {
+        result.errors.push(`No active social account found for channel ${channelId}`)
+        return result
+      }
+
+      // 3. Validate credentials
+      const credentials = account.credentials as {
+        accessToken?: string
+        refreshToken?: string
+      } | undefined
+
+      if (!credentials?.accessToken || !credentials?.refreshToken) {
+        result.errors.push('No valid API credentials on social account')
+        return result
+      }
+
+      // 4. Initialize YouTube client
+      const youtubeClient = new YouTubeClient(
+        {
+          clientId: process.env.GOOGLE_CLIENT_ID!,
+          clientSecret: process.env.GOOGLE_CLIENT_SECRET!,
+          accessToken: credentials.accessToken,
+          refreshToken: credentials.refreshToken,
+        },
+        this.payload,
+      )
+
+      // 5. Find all published/tracked videos with a YouTube videoId
+      const videos = await this.payload.find({
+        collection: 'youtube-content',
+        where: {
+          channel: { equals: channelId },
+          status: { in: ['published', 'tracked'] },
+        },
+        limit: 0,
+        depth: 0,
+      })
+
+      const videosWithYouTubeId = videos.docs.filter(
+        (video: any) => video.youtube?.videoId,
+      )
+
+      result.skippedCount = videos.docs.length - videosWithYouTubeId.length
+
+      if (videosWithYouTubeId.length === 0) {
+        result.success = true
+        return result
+      }
+
+      // 6. Batch videos into groups of 50 and fetch statistics
+      const batches = createBatches(videosWithYouTubeId, YOUTUBE_API_BATCH_LIMIT)
+
+      for (const batch of batches) {
+        try {
+          const videoIds = batch.map((video: any) => video.youtube.videoId as string)
+          const statistics = await youtubeClient.getVideoStatistics(videoIds)
+
+          // Build a lookup map for quick access
+          const statsMap = new Map(statistics.map((s) => [s.id, s]))
+
+          // 7. Update each video's performance fields
+          for (const video of batch) {
+            const youtubeVideoId = (video as any).youtube.videoId as string
+            const stats = statsMap.get(youtubeVideoId)
+
+            if (!stats) {
+              result.errors.push(
+                `No statistics returned for video ${youtubeVideoId} (doc ${video.id})`,
+              )
+              continue
+            }
+
+            try {
+              await this.payload.update({
+                collection: 'youtube-content',
+                id: video.id,
+                data: {
+                  performance: {
+                    views: stats.views,
+                    likes: stats.likes,
+                    comments: stats.comments,
+                    lastSyncedAt: new Date().toISOString(),
+                  },
+                },
+              })
+              result.syncedCount++
+            } catch (updateError) {
+              result.errors.push(
+                `Failed to update video ${video.id}: ${updateError}`,
+              )
+            }
+          }
+        } catch (batchError) {
+          result.errors.push(`Batch API call failed: ${batchError}`)
+        }
+      }
+
+      result.success = result.errors.length === 0
+    } catch (error) {
+      result.errors.push(`Sync error: ${error}`)
+    }
+
+    return result
+  }
+}
+
+/**
+ * Split an array into chunks of a given size.
+ */
+function createBatches<T>(items: T[], batchSize: number): T[][] {
+  const batches: T[][] = []
+  for (let i = 0; i < items.length; i += batchSize) {
+    batches.push(items.slice(i, i + batchSize))
+  }
+  return batches
+}
+
+export type { MetricsSyncResult }
diff --git a/tests/unit/youtube/video-metrics-sync.unit.spec.ts b/tests/unit/youtube/video-metrics-sync.unit.spec.ts
new file mode 100644
index 0000000..07e8464
--- /dev/null
+++ b/tests/unit/youtube/video-metrics-sync.unit.spec.ts
@@ -0,0 +1,357 @@
+/**
+ * VideoMetricsSyncService Unit Tests
+ *
+ * Tests the service that syncs video performance metrics from YouTube API
+ * to YouTubeContent.performance fields in the database.
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+// Mock YouTubeClient as a proper class before importing the service
+const mockGetVideoStatistics = vi.fn()
+
+vi.mock('@/lib/integrations/youtube/YouTubeClient', () => {
+  return {
+    YouTubeClient: class MockYouTubeClient {
+      getVideoStatistics = mockGetVideoStatistics
+    },
+  }
+})
+
+const mockFindByID = vi.fn()
+const mockFind = vi.fn()
+const mockUpdate = vi.fn()
+
+const mockPayload = {
+  findByID: mockFindByID,
+  find: mockFind,
+  update: mockUpdate,
+} as unknown as import('payload').Payload
+
+describe('VideoMetricsSyncService', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  function setupChannel(): void {
+    mockFindByID.mockResolvedValueOnce({
+      id: 1,
+      name: 'BlogWoman',
+      youtubeChannelId: 'UCxxx',
+    })
+  }
+
+  function setupSocialAccount(overrides?: Record<string, unknown>): void {
+    mockFind.mockResolvedValueOnce({
+      docs: [
+        {
+          id: 10,
+          credentials: {
+            accessToken: 'token-123',
+            refreshToken: 'refresh-456',
+          },
+          isActive: true,
+          ...overrides,
+        },
+      ],
+      totalDocs: 1,
+    })
+  }
+
+  function setupVideos(
+    videos: Array<{ id: number; youtube?: { videoId?: string }; status: string }>,
+  ): void {
+    mockFind.mockResolvedValueOnce({
+      docs: videos,
+      totalDocs: videos.length,
+    })
+  }
+
+  it('should sync metrics for published videos with YouTube videoId', async () => {
+    setupChannel()
+    setupSocialAccount()
+    setupVideos([
+      { id: 100, youtube: { videoId: 'yt-vid-1' }, status: 'published' },
+      { id: 101, youtube: { videoId: 'yt-vid-2' }, status: 'tracked' },
+    ])
+
+    mockGetVideoStatistics.mockResolvedValueOnce([
+      { id: 'yt-vid-1', views: 1500, likes: 120, comments: 45 },
+      { id: 'yt-vid-2', views: 3200, likes: 250, comments: 80 },
+    ])
+
+    mockUpdate.mockResolvedValue({})
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(true)
+    expect(result.syncedCount).toBe(2)
+    expect(result.skippedCount).toBe(0)
+    expect(result.errors).toHaveLength(0)
+
+    expect(mockUpdate).toHaveBeenCalledTimes(2)
+    expect(mockUpdate).toHaveBeenCalledWith(
+      expect.objectContaining({
+        collection: 'youtube-content',
+        id: 100,
+        data: expect.objectContaining({
+          performance: expect.objectContaining({
+            views: 1500,
+            likes: 120,
+            comments: 45,
+          }),
+        }),
+      }),
+    )
+    expect(mockUpdate).toHaveBeenCalledWith(
+      expect.objectContaining({
+        collection: 'youtube-content',
+        id: 101,
+        data: expect.objectContaining({
+          performance: expect.objectContaining({
+            views: 3200,
+            likes: 250,
+            comments: 80,
+          }),
+        }),
+      }),
+    )
+  })
+
+  it('should skip videos without a YouTube videoId', async () => {
+    setupChannel()
+    setupSocialAccount()
+    setupVideos([
+      { id: 100, youtube: { videoId: 'yt-vid-1' }, status: 'published' },
+      { id: 101, youtube: {}, status: 'published' },
+      { id: 102, status: 'published' },
+    ])
+
+    mockGetVideoStatistics.mockResolvedValueOnce([
+      { id: 'yt-vid-1', views: 500, likes: 40, comments: 10 },
+    ])
+
+    mockUpdate.mockResolvedValue({})
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(true)
+    expect(result.syncedCount).toBe(1)
+    expect(result.skippedCount).toBe(2)
+    expect(mockGetVideoStatistics).toHaveBeenCalledWith(['yt-vid-1'])
+  })
+
+  it('should return early with success when no videos exist', async () => {
+    setupChannel()
+    setupSocialAccount()
+    setupVideos([])
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(true)
+    expect(result.syncedCount).toBe(0)
+    expect(result.skippedCount).toBe(0)
+    expect(mockGetVideoStatistics).not.toHaveBeenCalled()
+  })
+
+  it('should return error when channel is not found', async () => {
+    mockFindByID.mockResolvedValueOnce(null)
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(999)
+
+    expect(result.success).toBe(false)
+    expect(result.errors).toContainEqual(
+      expect.stringContaining('not found'),
+    )
+    expect(mockFind).not.toHaveBeenCalled()
+  })
+
+  it('should return error when no active social account exists', async () => {
+    setupChannel()
+    mockFind.mockResolvedValueOnce({ docs: [], totalDocs: 0 })
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(false)
+    expect(result.errors).toContainEqual(
+      expect.stringContaining('No active social account'),
+    )
+  })
+
+  it('should return error when credentials are missing', async () => {
+    setupChannel()
+    setupSocialAccount({ credentials: {} })
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(false)
+    expect(result.errors).toContainEqual(
+      expect.stringContaining('No valid API credentials'),
+    )
+  })
+
+  it('should batch videos into groups of 50', async () => {
+    setupChannel()
+    setupSocialAccount()
+
+    // Create 75 videos to force 2 batches (50 + 25)
+    const videos = Array.from({ length: 75 }, (_, i) => ({
+      id: i + 1,
+      youtube: { videoId: `yt-vid-${i + 1}` },
+      status: 'published',
+    }))
+    setupVideos(videos)
+
+    // First batch: 50 videos
+    mockGetVideoStatistics.mockResolvedValueOnce(
+      Array.from({ length: 50 }, (_, i) => ({
+        id: `yt-vid-${i + 1}`,
+        views: 100,
+        likes: 10,
+        comments: 5,
+      })),
+    )
+
+    // Second batch: 25 videos
+    mockGetVideoStatistics.mockResolvedValueOnce(
+      Array.from({ length: 25 }, (_, i) => ({
+        id: `yt-vid-${i + 51}`,
+        views: 200,
+        likes: 20,
+        comments: 10,
+      })),
+    )
+
+    mockUpdate.mockResolvedValue({})
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(true)
+    expect(result.syncedCount).toBe(75)
+    expect(mockGetVideoStatistics).toHaveBeenCalledTimes(2)
+
+    const firstCallIds = mockGetVideoStatistics.mock.calls[0][0] as string[]
+    expect(firstCallIds).toHaveLength(50)
+
+    const secondCallIds = mockGetVideoStatistics.mock.calls[1][0] as string[]
+    expect(secondCallIds).toHaveLength(25)
+  })
+
+  it('should record errors for videos missing from API response', async () => {
+    setupChannel()
+    setupSocialAccount()
+    setupVideos([
+      { id: 100, youtube: { videoId: 'yt-vid-1' }, status: 'published' },
+      { id: 101, youtube: { videoId: 'yt-vid-2' }, status: 'published' },
+    ])
+
+    // Only return stats for one video
+    mockGetVideoStatistics.mockResolvedValueOnce([
+      { id: 'yt-vid-1', views: 500, likes: 40, comments: 10 },
+    ])
+
+    mockUpdate.mockResolvedValue({})
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(false)
+    expect(result.syncedCount).toBe(1)
+    expect(result.errors).toContainEqual(
+      expect.stringContaining('No statistics returned for video yt-vid-2'),
+    )
+  })
+
+  it('should handle API errors gracefully per batch', async () => {
+    setupChannel()
+    setupSocialAccount()
+    setupVideos([
+      { id: 100, youtube: { videoId: 'yt-vid-1' }, status: 'published' },
+    ])
+
+    mockGetVideoStatistics.mockRejectedValueOnce(new Error('API quota exceeded'))
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    const result = await service.syncMetrics(1)
+
+    expect(result.success).toBe(false)
+    expect(result.syncedCount).toBe(0)
+    expect(result.errors).toContainEqual(
+      expect.stringContaining('Batch API call failed'),
+    )
+  })
+
+  it('should set lastSyncedAt in performance data', async () => {
+    setupChannel()
+    setupSocialAccount()
+    setupVideos([
+      { id: 100, youtube: { videoId: 'yt-vid-1' }, status: 'published' },
+    ])
+
+    mockGetVideoStatistics.mockResolvedValueOnce([
+      { id: 'yt-vid-1', views: 100, likes: 10, comments: 5 },
+    ])
+
+    mockUpdate.mockResolvedValue({})
+
+    const { VideoMetricsSyncService } = await import(
+      '@/lib/integrations/youtube/VideoMetricsSyncService'
+    )
+
+    const service = new VideoMetricsSyncService(mockPayload)
+    await service.syncMetrics(1)
+
+    expect(mockUpdate).toHaveBeenCalledWith(
+      expect.objectContaining({
+        data: expect.objectContaining({
+          performance: expect.objectContaining({
+            lastSyncedAt: expect.any(String),
+          }),
+        }),
+      }),
+    )
+  })
+})