diff --git a/dev-packages/browser-integration-tests/suites/replay/bufferModeManual/test.ts b/dev-packages/browser-integration-tests/suites/replay/bufferModeManual/test.ts
index 09fc602d92b7..4ac7b9ea9cf1 100644
--- a/dev-packages/browser-integration-tests/suites/replay/bufferModeManual/test.ts
+++ b/dev-packages/browser-integration-tests/suites/replay/bufferModeManual/test.ts
@@ -287,6 +287,125 @@ sentryTest(
   },
 );
 
+sentryTest(
+  '[buffer-mode] manually starting replay ignores earlier performance entries',
+  async ({ getLocalTestUrl, page, browserName }) => {
+    // This was sometimes flaky on webkit, so skipping for now
+    if (shouldSkipReplayTest() || browserName === 'webkit') {
+      sentryTest.skip();
+    }
+
+    const reqPromise0 = waitForReplayRequest(page, 0);
+
+    await page.route('https://dsn.ingest.sentry.io/**/*', route => {
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify({ id: 'test-id' }),
+      });
+    });
+
+    const url = await getLocalTestUrl({ testDir: __dirname });
+
+    await page.goto(url);
+
+    // Wait for everything to be initialized - Replay is not running yet
+    await page.waitForFunction('!!window.Replay');
+
+    // Wait for a second, then start replay
+    await new Promise(resolve => setTimeout(resolve, 1000));
+    await page.evaluate('window.Replay.start()');
+
+    const req0 = await reqPromise0;
+
+    const event0 = getReplayEvent(req0);
+    const content0 = getReplayRecordingContent(req0);
+
+    expect(event0).toEqual(
+      getExpectedReplayEvent({
+        replay_type: 'session',
+      }),
+    );
+
+    const { performanceSpans } = content0;
+
+    // Here, we test that this does not contain any web-vital etc. performance spans
+    // as these have been emitted _before_ the replay was manually started
+    expect(performanceSpans).toEqual([
+      {
+        op: 'memory',
+        description: 'memory',
+        startTimestamp: expect.any(Number),
+        endTimestamp: expect.any(Number),
+        data: {
+          memory: {
+            jsHeapSizeLimit: expect.any(Number),
+            totalJSHeapSize: expect.any(Number),
+            usedJSHeapSize: expect.any(Number),
+          },
+        },
+      },
+    ]);
+  },
+);
+
+sentryTest(
+  '[buffer-mode] manually starting replay ignores earlier performance entries when starting immediately',
+  async ({ getLocalTestUrl, page, browserName }) => {
+    // This was sometimes flaky on webkit, so skipping for now
+    if (shouldSkipReplayTest() || browserName === 'webkit') {
+      sentryTest.skip();
+    }
+
+    const reqPromise0 = waitForReplayRequest(page, 0);
+
+    await page.route('https://dsn.ingest.sentry.io/**/*', route => {
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify({ id: 'test-id' }),
+      });
+    });
+
+    const url = await getLocalTestUrl({ testDir: __dirname });
+
+    page.goto(url);
+
+    // Wait for everything to be initialized, then start replay as soon as possible
+    await page.waitForFunction('!!window.Replay');
+    await page.evaluate('window.Replay.start()');
+
+    const req0 = await reqPromise0;
+
+    const event0 = getReplayEvent(req0);
+    const content0 = getReplayRecordingContent(req0);
+
+    expect(event0).toEqual(
+      getExpectedReplayEvent({
+        replay_type: 'session',
+      }),
+    );
+
+    const { performanceSpans } = content0;
+
+    expect(performanceSpans).toEqual([
+      {
+        op: 'memory',
+        description: 'memory',
+        startTimestamp: expect.any(Number),
+        endTimestamp: expect.any(Number),
+        data: {
+          memory: {
+            jsHeapSizeLimit: expect.any(Number),
+            totalJSHeapSize: expect.any(Number),
+            usedJSHeapSize: expect.any(Number),
+          },
+        },
+      },
+    ]);
+  },
+);
+
 // Doing this in buffer mode to test changing error sample rate after first
 // error happens.
 sentryTest(
diff --git a/packages/replay-internal/src/replay.ts b/packages/replay-internal/src/replay.ts
index 563938fe4d43..cfd8a2a45c33 100644
--- a/packages/replay-internal/src/replay.ts
+++ b/packages/replay-internal/src/replay.ts
@@ -1046,11 +1046,22 @@ export class ReplayContainer implements ReplayContainerInterface {
    * are included in the replay event before it is finished and sent to Sentry.
    */
   private _addPerformanceEntries(): Promise<Array<AddEventResult | null>> {
-    const performanceEntries = createPerformanceEntries(this.performanceEntries).concat(this.replayPerformanceEntries);
+    let performanceEntries = createPerformanceEntries(this.performanceEntries).concat(this.replayPerformanceEntries);
 
     this.performanceEntries = [];
     this.replayPerformanceEntries = [];
 
+    // If we are manually starting, we want to ensure we only include performance entries
+    // that are after the initial timestamp
+    // The reason for this is that we may have performance entries from the page load, but may decide to start
+    // the replay later on, in which case we do not want to include these entries.
+    // without this, manually started replays can have events long before the actual replay recording starts,
+    // which messes with the timeline etc.
+    if (this._requiresManualStart) {
+      const initialTimestampInSeconds = this._context.initialTimestamp / 1000;
+      performanceEntries = performanceEntries.filter(entry => entry.start >= initialTimestampInSeconds);
+    }
+
     return Promise.all(createPerformanceSpans(this, performanceEntries));
   }