diff --git a/dom/serviceworkers/PServiceWorkerRegistration.ipdl b/dom/serviceworkers/PServiceWorkerRegistration.ipdl
index 9b6814b0c221..36812b86a939 100644
--- a/dom/serviceworkers/PServiceWorkerRegistration.ipdl
+++ b/dom/serviceworkers/PServiceWorkerRegistration.ipdl
@@ -16,6 +16,7 @@ protocol PServiceWorkerRegistration
 parent:
   async Teardown();
 
+  async Unregister() returns (bool aSuccess, CopyableErrorResult aRv);
   async Update() returns (IPCServiceWorkerRegistrationDescriptorOrCopyableErrorResult aResult);
 
 child:
diff --git a/dom/serviceworkers/RemoteServiceWorkerRegistrationImpl.cpp b/dom/serviceworkers/RemoteServiceWorkerRegistrationImpl.cpp
index 7833bcc366f9..188a5ca2c14e 100644
--- a/dom/serviceworkers/RemoteServiceWorkerRegistrationImpl.cpp
+++ b/dom/serviceworkers/RemoteServiceWorkerRegistrationImpl.cpp
@@ -85,7 +85,25 @@ void
 RemoteServiceWorkerRegistrationImpl::Unregister(ServiceWorkerBoolCallback&& aSuccessCB,
                                                 ServiceWorkerFailureCallback&& aFailureCB)
 {
-  // TODO
+  if (!mActor) {
+    aFailureCB(CopyableErrorResult(NS_ERROR_DOM_INVALID_STATE_ERR));
+    return;
+  }
+
+  mActor->SendUnregister(
+    [successCB = std::move(aSuccessCB), aFailureCB]
+    (Tuple<bool, CopyableErrorResult>&& aResult) {
+    if (Get<1>(aResult).Failed()) {
+      // application layer error
+      aFailureCB(Get<1>(aResult));
+      return;
+    }
+    // success
+    successCB(Get<0>(aResult));
+  }, [aFailureCB] (ResponseRejectReason aReason) {
+    // IPC layer error
+    aFailureCB(CopyableErrorResult(NS_ERROR_DOM_INVALID_STATE_ERR));
+  });
 }
 
 RemoteServiceWorkerRegistrationImpl::RemoteServiceWorkerRegistrationImpl(const ServiceWorkerRegistrationDescriptor& aDescriptor)
diff --git a/dom/serviceworkers/ServiceWorkerRegistrationParent.cpp b/dom/serviceworkers/ServiceWorkerRegistrationParent.cpp
index 32860ee9a33e..0e9c80c6a1c4 100644
--- a/dom/serviceworkers/ServiceWorkerRegistrationParent.cpp
+++ b/dom/serviceworkers/ServiceWorkerRegistrationParent.cpp
@@ -29,6 +29,36 @@ ServiceWorkerRegistrationParent::RecvTeardown()
   return IPC_OK();
 }
 
+namespace {
+
+void
+ResolveUnregister(PServiceWorkerRegistrationParent::UnregisterResolver&& aResolver,
+                  bool aSuccess, nsresult aRv)
+{
+  aResolver(Tuple<const bool&, const CopyableErrorResult&>(
+    aSuccess, CopyableErrorResult(aRv)));
+}
+
+} // anonymous namespace
+
+IPCResult
+ServiceWorkerRegistrationParent::RecvUnregister(UnregisterResolver&& aResolver)
+{
+  if (!mProxy) {
+    ResolveUnregister(std::move(aResolver), false, NS_ERROR_DOM_INVALID_STATE_ERR);
+    return IPC_OK();
+  }
+
+  mProxy->Unregister()->Then(GetCurrentThreadSerialEventTarget(), __func__,
+    [aResolver] (bool aSuccess) mutable {
+      ResolveUnregister(std::move(aResolver), aSuccess, NS_OK);
+    }, [aResolver] (nsresult aRv) mutable {
+      ResolveUnregister(std::move(aResolver), false, aRv);
+    });
+
+  return IPC_OK();
+}
+
 IPCResult
 ServiceWorkerRegistrationParent::RecvUpdate(UpdateResolver&& aResolver)
 {
diff --git a/dom/serviceworkers/ServiceWorkerRegistrationParent.h b/dom/serviceworkers/ServiceWorkerRegistrationParent.h
index fea090194e21..a1be6808defa 100644
--- a/dom/serviceworkers/ServiceWorkerRegistrationParent.h
+++ b/dom/serviceworkers/ServiceWorkerRegistrationParent.h
@@ -27,6 +27,9 @@ class ServiceWorkerRegistrationParent final : public PServiceWorkerRegistrationP
   mozilla::ipc::IPCResult
   RecvTeardown() override;
 
+  mozilla::ipc::IPCResult
+  RecvUnregister(UnregisterResolver&& aResolver) override;
+
   mozilla::ipc::IPCResult
   RecvUpdate(UpdateResolver&& aResolver) override;
 
diff --git a/dom/serviceworkers/ServiceWorkerRegistrationProxy.cpp b/dom/serviceworkers/ServiceWorkerRegistrationProxy.cpp
index e574ff65bae6..516cc382a518 100644
--- a/dom/serviceworkers/ServiceWorkerRegistrationProxy.cpp
+++ b/dom/serviceworkers/ServiceWorkerRegistrationProxy.cpp
@@ -172,6 +172,78 @@ ServiceWorkerRegistrationProxy::RevokeActor(ServiceWorkerRegistrationParent* aAc
 
 namespace {
 
+class UnregisterCallback final : public nsIServiceWorkerUnregisterCallback
+{
+  RefPtr<GenericPromise::Private> mPromise;
+
+  ~UnregisterCallback() = default;
+
+public:
+  explicit UnregisterCallback(GenericPromise::Private* aPromise)
+    : mPromise(aPromise)
+  {
+    MOZ_DIAGNOSTIC_ASSERT(mPromise);
+  }
+
+  NS_IMETHOD
+  UnregisterSucceeded(bool aState) override
+  {
+    mPromise->Resolve(aState, __func__);
+    return NS_OK;
+  }
+
+  NS_IMETHOD
+  UnregisterFailed() override
+  {
+    mPromise->Reject(NS_ERROR_DOM_SECURITY_ERR, __func__);
+    return NS_OK;
+  }
+
+  NS_DECL_ISUPPORTS
+};
+
+NS_IMPL_ISUPPORTS(UnregisterCallback, nsIServiceWorkerUnregisterCallback)
+
+} // anonymous namespace
+
+RefPtr<GenericPromise>
+ServiceWorkerRegistrationProxy::Unregister()
+{
+  AssertIsOnBackgroundThread();
+
+  RefPtr<ServiceWorkerRegistrationProxy> self = this;
+  RefPtr<GenericPromise::Private> promise =
+    new GenericPromise::Private(__func__);
+
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(__func__,
+    [self, promise] () mutable {
+      nsresult rv = NS_ERROR_DOM_INVALID_STATE_ERR;
+      auto scopeExit = MakeScopeExit([&] {
+        promise->Reject(rv, __func__);
+      });
+
+      NS_ENSURE_TRUE_VOID(self->mReg);
+
+      RefPtr<ServiceWorkerManager> swm = ServiceWorkerManager::GetInstance();
+      NS_ENSURE_TRUE_VOID(swm);
+
+      RefPtr<UnregisterCallback> cb = new UnregisterCallback(promise);
+
+      rv = swm->Unregister(self->mReg->Principal(), cb,
+                           NS_ConvertUTF8toUTF16(self->mReg->Scope()));
+      NS_ENSURE_SUCCESS_VOID(rv);
+
+
+      scopeExit.release();
+    });
+
+  MOZ_ALWAYS_SUCCEEDS(SystemGroup::Dispatch(TaskCategory::Other, r.forget()));
+
+  return promise;
+}
+
+namespace {
+
 class UpdateCallback final : public ServiceWorkerUpdateFinishCallback
 {
   RefPtr<ServiceWorkerRegistrationPromise::Private> mPromise;
diff --git a/dom/serviceworkers/ServiceWorkerRegistrationProxy.h b/dom/serviceworkers/ServiceWorkerRegistrationProxy.h
index f5bbcec93aeb..64d3985214ae 100644
--- a/dom/serviceworkers/ServiceWorkerRegistrationProxy.h
+++ b/dom/serviceworkers/ServiceWorkerRegistrationProxy.h
@@ -72,6 +72,9 @@ public:
   void
   RevokeActor(ServiceWorkerRegistrationParent* aActor);
 
+  RefPtr<GenericPromise>
+  Unregister();
+
   RefPtr<ServiceWorkerRegistrationPromise>
   Update();