diff --git a/envoy/upstream/cluster_manager.h b/envoy/upstream/cluster_manager.h
index c751bfa9c286f..20ca0acca4df0 100644
--- a/envoy/upstream/cluster_manager.h
+++ b/envoy/upstream/cluster_manager.h
@@ -313,8 +313,14 @@ class ClusterManager {
 
   /**
    * Drain all connection pool connections owned by this cluster.
+   * @param cluster, the cluster to drain.
    */
   virtual void drainConnections(const std::string& cluster) PURE;
+
+  /**
+   * Drain all connection pool connections owned by all clusters in the cluster manager.
+   */
+  virtual void drainConnections() PURE;
 };
 
 using ClusterManagerPtr = std::unique_ptr<ClusterManager>;
diff --git a/source/common/upstream/cluster_manager_impl.cc b/source/common/upstream/cluster_manager_impl.cc
index 0943c0be4d662..f0a1d07cc0525 100644
--- a/source/common/upstream/cluster_manager_impl.cc
+++ b/source/common/upstream/cluster_manager_impl.cc
@@ -965,6 +965,14 @@ void ClusterManagerImpl::drainConnections(const std::string& cluster) {
   });
 }
 
+void ClusterManagerImpl::drainConnections() {
+  tls_.runOnAllThreads([](OptRef<ThreadLocalClusterManagerImpl> cluster_manager) {
+    for (const auto& cluster_entry : cluster_manager->thread_local_clusters_) {
+      cluster_entry.second->drainConnPools();
+    }
+  });
+}
+
 void ClusterManagerImpl::postThreadLocalRemoveHosts(const Cluster& cluster,
                                                     const HostVector& hosts_removed) {
   tls_.runOnAllThreads([name = cluster.info()->name(),
diff --git a/source/common/upstream/cluster_manager_impl.h b/source/common/upstream/cluster_manager_impl.h
index 5bb3e1dff6463..3b3cc3e225f3c 100644
--- a/source/common/upstream/cluster_manager_impl.h
+++ b/source/common/upstream/cluster_manager_impl.h
@@ -317,6 +317,8 @@ class ClusterManagerImpl : public ClusterManager, Logger::Loggable<Logger::Id::u
 
   void drainConnections(const std::string& cluster) override;
 
+  void drainConnections() override;
+
 protected:
   virtual void postThreadLocalRemoveHosts(const Cluster& cluster, const HostVector& hosts_removed);
 
diff --git a/test/integration/http_conn_pool_integration_test.cc b/test/integration/http_conn_pool_integration_test.cc
index a012da1e197fe..8f94fa0533005 100644
--- a/test/integration/http_conn_pool_integration_test.cc
+++ b/test/integration/http_conn_pool_integration_test.cc
@@ -16,10 +16,11 @@ class HttpConnPoolIntegrationTest : public HttpProtocolIntegrationTest {
       envoy::config::cluster::v3::CircuitBreakers circuit_breakers;
       auto* threshold = circuit_breakers.mutable_thresholds()->Add();
       threshold->mutable_max_connection_pools()->set_value(1);
-      bootstrap.mutable_static_resources()
-          ->mutable_clusters(0)
-          ->mutable_circuit_breakers()
-          ->MergeFrom(circuit_breakers);
+      auto* static_resources = bootstrap.mutable_static_resources();
+      for (int i = 0; i < static_resources->clusters_size(); ++i) {
+        static_resources->mutable_clusters(i)->mutable_circuit_breakers()->MergeFrom(
+            circuit_breakers);
+      }
     });
     HttpProtocolIntegrationTest::initialize();
   }
@@ -88,7 +89,7 @@ TEST_P(HttpConnPoolIntegrationTest, PoolCleanupAfterRemoteClose) {
 }
 
 // Verify that the drainConnections() cluster manager API works correctly.
-TEST_P(HttpConnPoolIntegrationTest, PoolDrainAfterDrainApi) {
+TEST_P(HttpConnPoolIntegrationTest, PoolDrainAfterDrainApiSpecificCluster) {
   initialize();
 
   codec_client_ = makeHttpConnection(lookupPort("http"));
@@ -115,5 +116,68 @@ TEST_P(HttpConnPoolIntegrationTest, PoolDrainAfterDrainApi) {
   test_server_->waitForGaugeEq("cluster.cluster_0.circuit_breakers.default.cx_pool_open", 0);
 }
 
+// Verify that the drainConnections() cluster manager API works correctly.
+TEST_P(HttpConnPoolIntegrationTest, PoolDrainAfterDrainApiAllClusters) {
+  config_helper_.addConfigModifier([](envoy::config::bootstrap::v3::Bootstrap& bootstrap) {
+    bootstrap.mutable_static_resources()->mutable_clusters()->Add()->MergeFrom(
+        *bootstrap.mutable_static_resources()->mutable_clusters(0));
+    bootstrap.mutable_static_resources()->mutable_clusters(1)->set_name("cluster_1");
+  });
+
+  setUpstreamCount(2);
+
+  auto host = config_helper_.createVirtualHost("cluster_1.com", "/", "cluster_1");
+  config_helper_.addVirtualHost(host);
+
+  config_helper_.setDefaultHostAndRoute("cluster_0.com", "/");
+
+  initialize();
+
+  // Request Flow to cluster_0.
+  codec_client_ = makeHttpConnection(lookupPort("http"));
+  default_request_headers_.setHost("cluster_0.com");
+  auto response = codec_client_->makeRequestWithBody(default_request_headers_, 1024);
+  waitForNextUpstreamRequest();
+
+  // Validate that the circuit breaker config is setup as we expect.
+  test_server_->waitForGaugeEq("cluster.cluster_0.circuit_breakers.default.cx_pool_open", 1);
+
+  upstream_request_->encodeHeaders(default_response_headers_, false);
+  upstream_request_->encodeData(512, true);
+  ASSERT_TRUE(response->waitForEndStream());
+
+  EXPECT_TRUE(upstream_request_->complete());
+  EXPECT_TRUE(response->complete());
+
+  auto first_connection = std::move(fake_upstream_connection_);
+  codec_client_->close();
+
+  // Request Flow to cluster_1.
+  codec_client_ = makeHttpConnection(lookupPort("http"));
+  default_request_headers_.setHost("cluster_1.com");
+  response = codec_client_->makeRequestWithBody(default_request_headers_, 1024);
+  waitForNextUpstreamRequest(1);
+
+  // Validate that the circuit breaker config is setup as we expect.
+  test_server_->waitForGaugeEq("cluster.cluster_1.circuit_breakers.default.cx_pool_open", 1);
+
+  upstream_request_->encodeHeaders(default_response_headers_, false);
+  upstream_request_->encodeData(512, true);
+  ASSERT_TRUE(response->waitForEndStream());
+
+  EXPECT_TRUE(upstream_request_->complete());
+  EXPECT_TRUE(response->complete());
+
+  // Drain connection pools via API. Need to post this to the server thread.
+  test_server_->server().dispatcher().post(
+      [this] { test_server_->server().clusterManager().drainConnections(); });
+
+  ASSERT_TRUE(first_connection->waitForDisconnect());
+  ASSERT_TRUE(fake_upstream_connection_->waitForDisconnect());
+
+  test_server_->waitForGaugeEq("cluster.cluster_0.circuit_breakers.default.cx_pool_open", 0);
+  test_server_->waitForGaugeEq("cluster.cluster_1.circuit_breakers.default.cx_pool_open", 0);
+}
+
 } // namespace
 } // namespace Envoy
diff --git a/test/mocks/upstream/cluster_manager.h b/test/mocks/upstream/cluster_manager.h
index 312a8d71822bd..f8b43ddb76557 100644
--- a/test/mocks/upstream/cluster_manager.h
+++ b/test/mocks/upstream/cluster_manager.h
@@ -69,6 +69,7 @@ class MockClusterManager : public ClusterManager {
     return cluster_timeout_budget_stat_names_;
   }
   MOCK_METHOD(void, drainConnections, (const std::string& cluster));
+  MOCK_METHOD(void, drainConnections, ());
 
   NiceMock<MockThreadLocalCluster> thread_local_cluster_;
   envoy::config::core::v3::BindConfig bind_config_;