diff --git a/extensions/amp-video/0.1/test/test-video-cache.js b/extensions/amp-video/0.1/test/test-video-cache.js
index 1b0d5ebfa1c4..6d71412291ae 100644
--- a/extensions/amp-video/0.1/test/test-video-cache.js
+++ b/extensions/amp-video/0.1/test/test-video-cache.js
@@ -78,6 +78,21 @@ describes.realWin('amp-video cached-sources', {amp: true}, (env) => {
         'https://example-com.cdn.ampproject.org/mbv/s/example.com/video2.mp4?amp_video_host_url=https%3A%2F%2Fcanonical.com'
       );
     });
+
+    it('should select the video[src] and never the sources children', async () => {
+      const videoEl = createVideo([
+        {src: 'video2.mp4'},
+        {src: 'video3.mp4', type: 'video/mp4'},
+      ]);
+      videoEl.setAttribute('src', 'video1.mp4');
+      const xhrSpy = env.sandbox.spy(xhrService, 'fetch');
+
+      await fetchCachedSources(videoEl, env.win);
+
+      expect(xhrSpy).to.have.been.calledWith(
+        'https://example-com.cdn.ampproject.org/mbv/s/example.com/video1.mp4?amp_video_host_url=https%3A%2F%2Fcanonical.com'
+      );
+    });
   });
 
   describe('url forming', () => {
@@ -145,6 +160,56 @@ describes.realWin('amp-video cached-sources', {amp: true}, (env) => {
       expect(addedSources[1].getAttribute('data-bitrate')).to.equal('1500');
       expect(addedSources[2].getAttribute('data-bitrate')).to.equal('700');
     });
+
+    it('should add video[src] as the last fallback source', async () => {
+      env.sandbox.stub(xhrService, 'fetch').resolves({
+        json: () =>
+          Promise.resolve({
+            sources: [
+              {'url': 'video1.mp4', 'bitrate_kbps': 700, type: 'video/mp4'},
+              {'url': 'video2.mp4', 'bitrate_kbps': 2000, type: 'video/mp4'},
+              {'url': 'video3.mp4', 'bitrate_kbps': 1500, type: 'video/mp4'},
+            ],
+          }),
+      });
+
+      const videoEl = createVideo([{src: 'video.mp4'}]);
+      videoEl.setAttribute('src', 'video1.mp4');
+      videoEl.setAttribute('type', 'video/mp4');
+
+      await fetchCachedSources(videoEl, env.win);
+
+      const lastSource = videoEl.querySelector('source:last-of-type');
+      expect(lastSource.getAttribute('src')).to.equal('video1.mp4');
+      expect(lastSource.getAttribute('type')).to.equal('video/mp4');
+    });
+
+    it('should clear the unused sources when video[src]', async () => {
+      env.sandbox.stub(xhrService, 'fetch').resolves({
+        json: () =>
+          Promise.resolve({
+            sources: [
+              {'url': 'video1.mp4', 'bitrate_kbps': 700, type: 'video/mp4'},
+              {'url': 'video2.mp4', 'bitrate_kbps': 2000, type: 'video/mp4'},
+              {'url': 'video3.mp4', 'bitrate_kbps': 1500, type: 'video/mp4'},
+            ],
+          }),
+      });
+
+      const videoEl = createVideo([
+        {src: 'video.mp4'},
+        {src: 'video.mp4'},
+        {src: 'video.mp4'},
+        {src: 'video.mp4'},
+        {src: 'video.mp4'},
+      ]);
+      videoEl.setAttribute('src', 'video1.mp4');
+
+      await fetchCachedSources(videoEl, env.win);
+
+      const addedSources = videoEl.querySelectorAll('source');
+      expect(addedSources).to.have.lengthOf(4); // 3 from cache + 1 fallback.
+    });
   });
 
   describe('end to end', () => {
diff --git a/extensions/amp-video/0.1/video-cache.js b/extensions/amp-video/0.1/video-cache.js
index c8019a2b5604..56c30c7dbc63 100644
--- a/extensions/amp-video/0.1/video-cache.js
+++ b/extensions/amp-video/0.1/video-cache.js
@@ -16,7 +16,12 @@
 
 import {Services} from '../../../src/services';
 import {addParamsToUrl, resolveRelativeUrl} from '../../../src/url';
-import {createElementWithAttributes, matches} from '../../../src/dom';
+import {
+  createElementWithAttributes,
+  iterateCursor,
+  matches,
+  removeElement,
+} from '../../../src/dom';
 import {extensionScriptInNode} from '../../../src/service/extension-script';
 import {toArray} from '../../../src/core/types/array';
 import {user} from '../../../src/log';
@@ -33,13 +38,17 @@ import {user} from '../../../src/log';
 export function fetchCachedSources(videoEl, win) {
   if (
     !extensionScriptInNode(win, 'amp-cache-url', '0.1') ||
-    !videoEl.querySelector('source[src]').getAttribute('src')
+    !(
+      videoEl.getAttribute('src') ||
+      videoEl.querySelector('source[src]')?.getAttribute('src')
+    )
   ) {
     user().error('AMP-VIDEO', 'Video cache not properly configured');
     return Promise.resolve();
   }
   const {canonicalUrl, sourceUrl} = Services.documentInfoForDoc(win.document);
   const servicePromise = Services.cacheUrlServicePromiseForDoc(videoEl);
+  maybeReplaceSrcWithSourceElement(videoEl, win);
   const videoUrl = resolveRelativeUrl(selectVideoSource(videoEl), sourceUrl);
   return servicePromise
     .then((service) => service.createCacheUrl(videoUrl))
@@ -95,3 +104,34 @@ function applySourcesToVideo(videoEl, sources) {
       videoEl.insertBefore(sourceEl, videoEl.firstChild);
     });
 }
+
+/**
+ * If present, moves the src attribute to a source element to enable playing
+ * from multiple sources: the cached ones and the fallback initial src.
+ * @param {!Element} videoEl
+ * @param {!Window} win
+ */
+function maybeReplaceSrcWithSourceElement(videoEl, win) {
+  if (!videoEl.hasAttribute('src')) {
+    return;
+  }
+  const sourceEl = win.document.createElement('source');
+  const srcAttr = videoEl.getAttribute('src');
+  sourceEl.setAttribute('src', srcAttr);
+
+  const typeAttr = videoEl.getAttribute('type');
+  if (typeAttr) {
+    sourceEl.setAttribute('type', typeAttr);
+  }
+
+  // Remove the src attr so the source children can play.
+  videoEl.removeAttribute('src');
+  videoEl.removeAttribute('type');
+
+  // Remove all existing sources as they are never supposed to play for a video
+  // that has a src, cf https://html.spec.whatwg.org/#concept-media-load-algorithm
+  const sourceEls = videoEl.querySelectorAll('source');
+  iterateCursor(sourceEls, (el) => removeElement(el));
+
+  videoEl.insertBefore(sourceEl, videoEl.firstChild);
+}