diff --git a/CHANGES.md b/CHANGES.md
index 7bb566be6e57..c02e3b4b552e 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -14,6 +14,7 @@ Change Log
    * `Scene/PerspectiveFrustum` is deprecated and will be removed in 1.38. Use `Core/PerspectiveFrustum`.
    * `Scene/PerspectiveOffCenterFrustum` is deprecated and will be removed in 1.38. Use `Core/PerspectiveOffCenterFrustum`.
 * Added ability to show tile urls in the 3D Tiles Inspector. [#5592](https://github.com/AnalyticalGraphicsInc/cesium/pull/5592)
+* Fixed issue where composite 3D Tiles that contained instanced 3D Tiles with an external model reference would fail to download the model.
 * Added behavior to `Cesium3DTilesInspector` that selects the first tileset hovered over if no tilest is specified. [#5139](https://github.com/AnalyticalGraphicsInc/cesium/issues/5139)
 * Added ability to provide a `width` and `height` to `scene.pick`. [#5602](https://github.com/AnalyticalGraphicsInc/cesium/pull/5602)
 * Added setter for `GeoJsonDataSource.name` to specify a name for the datasource [#5653](https://github.com/AnalyticalGraphicsInc/cesium/issues/5653)
diff --git a/Source/Scene/Instanced3DModel3DTileContent.js b/Source/Scene/Instanced3DModel3DTileContent.js
index df1de7ca0593..66ad743fc5d2 100644
--- a/Source/Scene/Instanced3DModel3DTileContent.js
+++ b/Source/Scene/Instanced3DModel3DTileContent.js
@@ -308,6 +308,10 @@ define([
 
         if (gltfFormat === 0) {
             var gltfUrl = getStringFromTypedArray(gltfView);
+
+            // We need to remove padding from the end of the model URL in case this tile was part of a composite tile.
+            // This removes all white space and null characters from the end of the string.
+            gltfUrl = gltfUrl.replace(/[\s\0]+$/, '');
             collectionOptions.url = getAbsoluteUri(joinUrls(getBaseUri(content._url, true), gltfUrl));
         } else {
             collectionOptions.gltf = gltfView;
diff --git a/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/box.glb b/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/box.glb
new file mode 100644
index 000000000000..2bde3c4ee98e
Binary files /dev/null and b/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/box.glb differ
diff --git a/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/compositeOfInstanced.cmpt b/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/compositeOfInstanced.cmpt
new file mode 100644
index 000000000000..99f84f85f092
Binary files /dev/null and b/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/compositeOfInstanced.cmpt differ
diff --git a/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/tileset.json b/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/tileset.json
new file mode 100644
index 000000000000..9609546a000c
--- /dev/null
+++ b/Specs/Data/Cesium3DTiles/Composite/CompositeOfInstanced/tileset.json
@@ -0,0 +1,29 @@
+{
+  "asset": {
+    "version": "0.0"
+  },
+  "properties": {
+    "Height": {
+      "minimum": 20,
+      "maximum": 20
+    }
+  },
+  "geometricError": 70,
+  "root": {
+    "refine": "ADD",
+    "boundingVolume": {
+      "region": [
+        -1.3197004795898053,
+        0.6988582109,
+        -1.3196595204101946,
+        0.6988897891,
+        0,
+        30
+      ]
+    },
+    "geometricError": 0,
+    "content": {
+      "url": "compositeOfInstanced.cmpt"
+    }
+  }
+}
diff --git a/Specs/Scene/Composite3DTileContentSpec.js b/Specs/Scene/Composite3DTileContentSpec.js
index 103ad89ac774..2f0be37c6bed 100644
--- a/Specs/Scene/Composite3DTileContentSpec.js
+++ b/Specs/Scene/Composite3DTileContentSpec.js
@@ -20,12 +20,13 @@ defineSuite([
 
     var compositeUrl = './Data/Cesium3DTiles/Composite/Composite/';
     var compositeOfComposite = './Data/Cesium3DTiles/Composite/CompositeOfComposite/';
+    var compositeOfInstanced = './Data/Cesium3DTiles/Composite/compositeOfInstanced/';
 
     beforeAll(function() {
         scene = createScene();
         // One item in each data set is always located in the center, so point the camera there
         var center = Cartesian3.fromRadians(centerLongitude, centerLatitude);
-        scene.camera.lookAt(center, new HeadingPitchRange(0.0, -1.57, 30.0));
+        scene.camera.lookAt(center, new HeadingPitchRange(0.0, -1.57, 26.0));
     });
 
     afterAll(function() {
@@ -121,6 +122,10 @@ defineSuite([
         return Cesium3DTilesTester.loadTileset(scene, compositeOfComposite).then(expectRenderComposite);
     });
 
+    it('renders multiple instanced tilesets', function() {
+        return Cesium3DTilesTester.loadTileset(scene, compositeOfInstanced).then(expectRenderComposite);
+    });
+
     it('destroys', function() {
         return Cesium3DTilesTester.tileDestroys(scene, compositeUrl);
     });