diff --git a/dom/workers/test/browser.ini b/dom/workers/test/browser.ini
index d50e94c18c6c..12e0bb491ee0 100644
--- a/dom/workers/test/browser.ini
+++ b/dom/workers/test/browser.ini
@@ -22,3 +22,6 @@ support-files =
 support-files =
   file_service_worker.js
   file_service_worker_container.html
+[browser_serviceworker_fetch_new_process.js]
+support-files =
+  file_service_worker_fetch_synthetic.js
diff --git a/dom/workers/test/browser_serviceworker_fetch_new_process.js b/dom/workers/test/browser_serviceworker_fetch_new_process.js
new file mode 100644
index 000000000000..a1fe3b616b01
--- /dev/null
+++ b/dom/workers/test/browser_serviceworker_fetch_new_process.js
@@ -0,0 +1,151 @@
+const DIRPATH = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content/",
+  ""
+);
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.tabs.remote.separatePrivilegedMozillaWebContentProcess", true],
+      ["browser.tabs.remote.separatedMozillaDomains", "example.org"],
+      ["dom.ipc.processCount.privilegedmozilla", 1],
+      ["dom.ipc.processCount.webIsolated", 1],
+      ["dom.ipc.processPrelaunch.enabled", false],
+      ["dom.serviceWorkers.enabled", true],
+      ["dom.serviceWorkers.testing.enabled", true],
+      ["dom.serviceworkers.parent_intercept", true],
+    ],
+  });
+});
+
+function countRemoteType(remoteType) {
+  return ChromeUtils.getAllDOMProcesses().filter(
+    p => p.remoteType == remoteType
+  ).length;
+}
+
+async function waitForWorkerIdleShutdown(swRegInfo, remoteType) {
+  info(`waiting for ${remoteType} procs to shut down`);
+  ok(swRegInfo.activeWorker, "worker isn't currently active?");
+  is(
+    countRemoteType(remoteType),
+    1,
+    `should have a single ${remoteType} process`
+  );
+
+  // Let's not wait too long for the process to shutdown.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.serviceWorkers.idle_timeout", 0],
+      ["dom.serviceWorkers.idle_extended_timeout", 0],
+    ],
+  });
+
+  // We need to cause the worker to re-evaluate its idle timeout. The easiest
+  // way to do this I could think of is to attach and then detach the debugger
+  // from the active worker.
+  swRegInfo.activeWorker.attachDebugger();
+  await new Promise(resolve => Cu.dispatch(resolve));
+  swRegInfo.activeWorker.detachDebugger();
+
+  // Eventually the length will reach 0, meaning we're done!
+  await TestUtils.waitForCondition(
+    () => countRemoteType(remoteType) == 0,
+    "wait for the worker's process to shutdown"
+  );
+
+  is(
+    countRemoteType(remoteType),
+    0,
+    "processes with `remoteType` type should have shut down"
+  );
+
+  // Make sure we never kill workers on idle except when this is called.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.serviceWorkers.idle_timeout", 299999],
+      ["dom.serviceWorkers.idle_extended_timeout", 299999],
+    ],
+  });
+}
+
+async function do_test_sw(host, remoteType) {
+  info(`entering test: host=${host}, remoteType=${remoteType}`);
+
+  const prin = Services.scriptSecurityManager.createContentPrincipal(
+    Services.io.newURI(`https://${host}`),
+    {}
+  );
+  const sw = `https://${host}/${DIRPATH}file_service_worker_fetch_synthetic.js`;
+  const scope = `https://${host}/${DIRPATH}scope`;
+
+  const swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+    Ci.nsIServiceWorkerManager
+  );
+  const swRegInfo = await swm.registerForTest(prin, scope, sw);
+  swRegInfo.QueryInterface(Ci.nsIServiceWorkerRegistrationInfo);
+
+  info(
+    `service worker registered: ${JSON.stringify({
+      principal: swRegInfo.principal.spec,
+      scope: swRegInfo.scope,
+    })}`
+  );
+
+  // Wait for the worker to install & shut down.
+  await TestUtils.waitForCondition(
+    () => swRegInfo.activeWorker,
+    "wait for the worker to become active"
+  );
+  await waitForWorkerIdleShutdown(swRegInfo, remoteType);
+
+  await BrowserTestUtils.withNewTab("about:blank", async browser => {
+    // NOTE: We intentionally trigger the navigation from content in order to
+    // make sure frontend doesn't eagerly process-switch for us.
+    SpecialPowers.spawn(browser, [scope], async scope => {
+      content.location.href = `${scope}/intercepted.html`;
+    });
+    await BrowserTestUtils.browserLoaded(browser);
+
+    is(
+      countRemoteType(remoteType),
+      1,
+      "should have spawned a content process with the correct remoteType"
+    );
+
+    // Ensure the worker was loaded in this process.
+    const workerDebuggerURLs = await SpecialPowers.spawn(
+      browser,
+      [sw],
+      async url => {
+        await content.navigator.serviceWorker.ready;
+        const wdm = Cc[
+          "@mozilla.org/dom/workers/workerdebuggermanager;1"
+        ].getService(Ci.nsIWorkerDebuggerManager);
+
+        return Array.from(wdm.getWorkerDebuggerEnumerator())
+          .map(wd => {
+            return wd.url;
+          })
+          .filter(swURL => swURL == url);
+      }
+    );
+    Assert.deepEqual(
+      workerDebuggerURLs,
+      [sw],
+      "The worker should be running in the correct child process"
+    );
+
+    // Unregister the worker.
+    await SpecialPowers.spawn(browser, [], async () => {
+      let registration = await content.navigator.serviceWorker.ready;
+      await registration.unregister();
+    });
+  });
+
+  await waitForWorkerIdleShutdown(swRegInfo, remoteType);
+}
+
+add_task(async function test() {
+  await do_test_sw("example.org", "privilegedmozilla");
+});
diff --git a/dom/workers/test/file_service_worker_fetch_synthetic.js b/dom/workers/test/file_service_worker_fetch_synthetic.js
new file mode 100644
index 000000000000..46e991fd0f85
--- /dev/null
+++ b/dom/workers/test/file_service_worker_fetch_synthetic.js
@@ -0,0 +1,15 @@
+addEventListener("install", function(evt) {
+  evt.waitUntil(self.skipWaiting());
+});
+
+self.addEventListener("fetch", event => {
+  event.respondWith(
+    new Response(
+      `<!DOCTYPE HTML><body>
+        <h1 id="url">${event.request.url}</h1>
+        <h1 id="location">${self.location.href}</h1>
+      </body>`,
+      { headers: { "Content-Type": "text/html" } }
+    )
+  );
+});