diff --git a/content/browser/attribution_reporting/attribution_manager_impl.cc b/content/browser/attribution_reporting/attribution_manager_impl.cc
index 20c9c0f3b37ac..6537d8477c26e 100644
--- a/content/browser/attribution_reporting/attribution_manager_impl.cc
+++ b/content/browser/attribution_reporting/attribution_manager_impl.cc
@@ -958,7 +958,18 @@ void AttributionManagerImpl::RemoveAttributionDataByDataKey(
     base::OnceClosure callback) {
   attribution_storage_.AsyncCall(&AttributionStorage::DeleteByDataKey)
       .WithArgs(data_key)
-      .Then(std::move(callback));
+      .Then(std::move(callback).Then(
+          // TODO(crbug.com/1446693): Replace this lambda with
+          // `OnClearDataComplete()` so that observers are notified and the
+          // task-runner priority is restored.
+          base::BindOnce(
+              [](base::WeakPtr<AttributionManagerImpl> manager) {
+                if (manager) {
+                  manager->NotifySourcesChanged();
+                  manager->NotifyReportsChanged();
+                }
+              },
+              weak_factory_.GetWeakPtr())));
 }
 
 void AttributionManagerImpl::GetReportsToSend() {
diff --git a/content/browser/attribution_reporting/attribution_manager_impl_unittest.cc b/content/browser/attribution_reporting/attribution_manager_impl_unittest.cc
index e8eb487e940d5..7f75774a2e9be 100644
--- a/content/browser/attribution_reporting/attribution_manager_impl_unittest.cc
+++ b/content/browser/attribution_reporting/attribution_manager_impl_unittest.cc
@@ -61,6 +61,7 @@
 #include "content/browser/attribution_reporting/test/mock_content_browser_client.h"
 #include "content/browser/browsing_data/browsing_data_filter_builder_impl.h"
 #include "content/browser/storage_partition_impl.h"
+#include "content/public/browser/attribution_data_model.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browsing_data_filter_builder.h"
 #include "content/public/browser/global_routing_id.h"
@@ -2839,6 +2840,24 @@ TEST_F(AttributionManagerImplTest, PendingReportsMetrics_OverLimits) {
       (base::Seconds(10) * kMaxPendingReportsTimings).InMilliseconds());
 }
 
+TEST_F(AttributionManagerImplTest,
+       RemoveAttributionDataByDataKey_NotifiesObservers) {
+  MockAttributionObserver observer;
+  base::ScopedObservation<AttributionManager, AttributionObserver> observation(
+      &observer);
+  observation.Observe(attribution_manager_.get());
+
+  EXPECT_CALL(observer, OnSourcesChanged);
+  EXPECT_CALL(observer, OnReportsChanged);
+
+  base::RunLoop run_loop;
+  attribution_manager_->RemoveAttributionDataByDataKey(
+      AttributionDataModel::DataKey(
+          url::Origin::Create(GURL("https://x.test"))),
+      run_loop.QuitClosure());
+  run_loop.Run();
+}
+
 class AttributionManagerImplDebugReportTest
     : public AttributionManagerImplTest {
  protected: