diff --git a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/dart/controller/http/DartSqlResource.java b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/dart/controller/http/DartSqlResource.java
index 37e9f1051318..944711b90ccb 100644
--- a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/dart/controller/http/DartSqlResource.java
+++ b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/dart/controller/http/DartSqlResource.java
@@ -237,7 +237,10 @@ public Response cancelQuery(
 
     List<SqlLifecycleManager.Cancelable> cancelables = sqlLifecycleManager.getAll(sqlQueryId);
     if (cancelables.isEmpty()) {
-      return Response.status(Response.Status.NOT_FOUND).build();
+      // Return ACCEPTED even if the query wasn't found. When the Router broadcasts cancellation requests to all
+      // Brokers, this ensures the user sees a successful request.
+      AuthorizationUtils.setRequestAuthorizationAttributeIfNeeded(req);
+      return Response.status(Response.Status.ACCEPTED).build();
     }
 
     final Access access = authorizeCancellation(req, cancelables);
@@ -247,14 +250,12 @@ public Response cancelQuery(
 
       // Don't call cancel() on the cancelables. That just cancels native queries, which is useless here. Instead,
       // get the controller and stop it.
-      boolean found = false;
       for (SqlLifecycleManager.Cancelable cancelable : cancelables) {
         final HttpStatement stmt = (HttpStatement) cancelable;
         final Object dartQueryId = stmt.context().get(DartSqlEngine.CTX_DART_QUERY_ID);
         if (dartQueryId instanceof String) {
           final ControllerHolder holder = controllerRegistry.get((String) dartQueryId);
           if (holder != null) {
-            found = true;
             holder.cancel();
           }
         } else {
@@ -267,7 +268,9 @@ public Response cancelQuery(
         }
       }
 
-      return Response.status(found ? Response.Status.ACCEPTED : Response.Status.NOT_FOUND).build();
+      // Return ACCEPTED even if the query wasn't found. When the Router broadcasts cancellation requests to all
+      // Brokers, this ensures the user sees a successful request.
+      return Response.status(Response.Status.ACCEPTED).build();
     } else {
       return Response.status(Response.Status.FORBIDDEN).build();
     }
diff --git a/extensions-core/multi-stage-query/src/test/java/org/apache/druid/msq/dart/controller/http/DartSqlResourceTest.java b/extensions-core/multi-stage-query/src/test/java/org/apache/druid/msq/dart/controller/http/DartSqlResourceTest.java
index db3479178724..f297e670506e 100644
--- a/extensions-core/multi-stage-query/src/test/java/org/apache/druid/msq/dart/controller/http/DartSqlResourceTest.java
+++ b/extensions-core/multi-stage-query/src/test/java/org/apache/druid/msq/dart/controller/http/DartSqlResourceTest.java
@@ -724,7 +724,7 @@ public void test_cancelQuery_regularUser_unknownQuery()
            .thenReturn(makeAuthenticationResult(REGULAR_USER_NAME));
 
     final Response cancellationResponse = sqlResource.cancelQuery("nonexistent", httpServletRequest);
-    Assertions.assertEquals(Response.Status.NOT_FOUND.getStatusCode(), cancellationResponse.getStatus());
+    Assertions.assertEquals(Response.Status.ACCEPTED.getStatusCode(), cancellationResponse.getStatus());
   }
 
   /**