diff --git a/packages/@ember/-internals/routing/lib/system/route.ts b/packages/@ember/-internals/routing/lib/system/route.ts
index 77f85a3cb4b..0411715f2b5 100644
--- a/packages/@ember/-internals/routing/lib/system/route.ts
+++ b/packages/@ember/-internals/routing/lib/system/route.ts
@@ -1935,7 +1935,7 @@ interface PartialRenderOptions {
   model?: {};
 }
 
-function getFullQueryParams(router: EmberRouter, state: TransitionState<Route>) {
+export function getFullQueryParams(router: EmberRouter, state: TransitionState<Route>) {
   if (state['fullQueryParams']) {
     return state['fullQueryParams'];
   }
diff --git a/packages/@ember/-internals/routing/lib/system/router.ts b/packages/@ember/-internals/routing/lib/system/router.ts
index 8e08c6ca085..871c077c303 100644
--- a/packages/@ember/-internals/routing/lib/system/router.ts
+++ b/packages/@ember/-internals/routing/lib/system/router.ts
@@ -14,6 +14,7 @@ import { calculateCacheKey, extractRouteArgs, getActiveTargetName, resemblesURL
 import DSL from './dsl';
 import Route, {
   defaultSerialize,
+  getFullQueryParams,
   hasDefaultSerialize,
   RenderOptions,
   ROUTE_CONNECTIONS,
@@ -28,7 +29,6 @@ import { MatchCallback } from 'route-recognizer';
 import Router, {
   InternalRouteInfo,
   logAbort,
-  QUERY_PARAMS_SYMBOL,
   STATE_SYMBOL,
   Transition,
   TransitionError,
@@ -861,7 +861,7 @@ class EmberRouter extends EmberObject {
 
     let unchangedQPs = {};
     let qpUpdates = this._qpUpdates;
-    let params = this._routerMicrolib.activeTransition[QUERY_PARAMS_SYMBOL];
+    let params = getFullQueryParams(this, this._routerMicrolib.activeTransition[STATE_SYMBOL]);
     for (let key in params) {
       if (!qpUpdates.has(key)) {
         unchangedQPs[key] = params[key];
diff --git a/packages/ember/tests/routing/query_params_test.js b/packages/ember/tests/routing/query_params_test.js
index b73a3ea4a72..74071df660d 100644
--- a/packages/ember/tests/routing/query_params_test.js
+++ b/packages/ember/tests/routing/query_params_test.js
@@ -137,6 +137,55 @@ moduleFor(
       });
     }
 
+    ['@test Calling transitionTo does not serialize query params already serialized on the activeTransition'](
+      assert
+    ) {
+      assert.expect(3);
+
+      this.router.map(function () {
+        this.route('parent', function () {
+          this.route('child');
+          this.route('sibling');
+        });
+      });
+
+      this.add(
+        'route:parent.child',
+        Route.extend({
+          afterModel() {
+            this.transitionTo('parent.sibling');
+          },
+        })
+      );
+
+      this.add(
+        'controller:parent',
+        Controller.extend({
+          queryParams: ['array', 'string'],
+          array: [],
+          string: '',
+        })
+      );
+
+      // `/parent/child?array=["one",2]&string=hello`
+      return this.visit('/parent/child?array=%5B%22one%22%2C2%5D&string=hello').then(() => {
+        this.assertCurrentPath(
+          '/parent/sibling?array=%5B%22one%22%2C2%5D&string=hello',
+          'redirected to the sibling route, instead of child route'
+        );
+        assert.equal(
+          this.getController('parent').get('string'),
+          'hello',
+          'controller has value from the active transition'
+        );
+        assert.deepEqual(
+          this.getController('parent').get('array'),
+          ['one', 2],
+          'controller has value from the active transition'
+        );
+      });
+    }
+
     async ['@test Single query params can be set on the controller and reflected in the url'](
       assert
     ) {