diff --git a/vizro-core/changelog.d/20240311_161236_antony.milne_external_assets.md b/vizro-core/changelog.d/20240311_161236_antony.milne_external_assets.md
new file mode 100644
index 000000000..d5d10a7f1
--- /dev/null
+++ b/vizro-core/changelog.d/20240311_161236_antony.milne_external_assets.md
@@ -0,0 +1,47 @@
+<!--
+A new scriv changelog fragment.
+
+Uncomment the section that is right (remove the HTML comment wrapper).
+-->
+
+<!--
+### Highlights ✨
+
+- A bullet item for the Highlights ✨ category with a link to the relevant PR at the end of your entry, e.g. Enable feature XXX ([#1](https://github.com/mckinsey/vizro/pull/1))
+
+-->
+<!--
+### Removed
+
+- A bullet item for the Removed category with a link to the relevant PR at the end of your entry, e.g. Enable feature XXX ([#1](https://github.com/mckinsey/vizro/pull/1))
+
+-->
+<!--
+### Added
+
+- A bullet item for the Added category with a link to the relevant PR at the end of your entry, e.g. Enable feature XXX ([#1](https://github.com/mckinsey/vizro/pull/1))
+
+-->
+<!--
+### Changed
+
+- A bullet item for the Changed category with a link to the relevant PR at the end of your entry, e.g. Enable feature XXX ([#1](https://github.com/mckinsey/vizro/pull/1))
+
+-->
+<!--
+### Deprecated
+
+- A bullet item for the Deprecated category with a link to the relevant PR at the end of your entry, e.g. Enable feature XXX ([#1](https://github.com/mckinsey/vizro/pull/1))
+
+-->
+
+### Fixed
+
+- Fix path to built-in Vizro assets when `requests_pathname_prefix` is not the same as `routes_pathname_prefix` ([#358](https://github.com/mckinsey/vizro/pull/358))
+<!--
+
+### Security
+
+- A bullet item for the Security category with a link to the relevant PR at the end of your entry, e.g. Enable feature XXX ([#1](https://github.com/mckinsey/vizro/pull/1))
+
+-->
diff --git a/vizro-core/docs/pages/user-guides/run.md b/vizro-core/docs/pages/user-guides/run.md
index fbaa1be1e..5479d58be 100644
--- a/vizro-core/docs/pages/user-guides/run.md
+++ b/vizro-core/docs/pages/user-guides/run.md
@@ -124,4 +124,4 @@ A Vizro app wraps a Dash app, which itself wraps a Flask app. Hence to deploy a
 
 In particular, `app = Vizro()` exposes the Flask app through `app.dash.server`. As in the [above example with Gunicorn](#gunicorn), this provides the application instance to a WSGI server.
 
-[`Vizro`][vizro.Vizro] accepts `**kwargs` that are passed through to `Dash`. This allows you to configure the underlying Dash app using the same [argumentst that are available](https://dash.plotly.com/reference#dash.dash) in `Dash`. For example, in a deployment context, you might like to specify a custom `url_base_pathname` to serve your Vizro app at a specific URL rather than at your domain root.
+[`Vizro`][vizro.Vizro] accepts `**kwargs` that are passed through to `Dash`. This allows you to configure the underlying Dash app using the same [arguments that are available](https://dash.plotly.com/reference#dash.dash) in `Dash`. For example, in a deployment context, you might like to specify a custom `url_base_pathname` to serve your Vizro app at a specific URL rather than at your domain root.
diff --git a/vizro-core/src/vizro/_vizro.py b/vizro-core/src/vizro/_vizro.py
index d7a221fd1..d9703c247 100644
--- a/vizro-core/src/vizro/_vizro.py
+++ b/vizro-core/src/vizro/_vizro.py
@@ -37,11 +37,11 @@ def __init__(self, **kwargs):
         # Include Vizro assets (in the static folder) as external scripts and stylesheets. We extend self.dash.config
         # objects so the user can specify additional external_scripts and external_stylesheets via kwargs.
         vizro_assets_folder = Path(__file__).with_name("static")
-        static_url_path = self.dash.config.requests_pathname_prefix + STATIC_URL_PREFIX
-        vizro_css = self._get_external_assets(static_url_path, vizro_assets_folder, "css")
+        requests_pathname_prefix = self.dash.config.requests_pathname_prefix
+        vizro_css = [requests_pathname_prefix + path for path in self._get_external_assets(vizro_assets_folder, "css")]
         vizro_js = [
-            {"src": path, "type": "module"}
-            for path in self._get_external_assets(static_url_path, vizro_assets_folder, "js")
+            {"src": requests_pathname_prefix + path, "type": "module"}
+            for path in self._get_external_assets(vizro_assets_folder, "js")
         ]
         self.dash.config.external_stylesheets.extend(vizro_css)
         self.dash.config.external_scripts.extend(vizro_js)
@@ -49,13 +49,14 @@ def __init__(self, **kwargs):
         # Serve all assets (including files other than css and js) that live in vizro_assets_folder at the
         # route /vizro. Based on code in Dash.init_app that serves assets_folder. This respects the case that the
         # dashboard is not hosted at the root of the server, e.g. http://www.example.com/dashboard/vizro.
-        blueprint_prefix = self.dash.config.routes_pathname_prefix.replace("/", "_").replace(".", "_")
+        routes_pathname_prefix = self.dash.config.routes_pathname_prefix
+        blueprint_prefix = routes_pathname_prefix.replace("/", "_").replace(".", "_")
         self.dash.server.register_blueprint(
             flask.Blueprint(
                 f"{blueprint_prefix}vizro_assets",
                 self.dash.config.name,
                 static_folder=vizro_assets_folder,
-                static_url_path=static_url_path,
+                static_url_path=routes_pathname_prefix + STATIC_URL_PREFIX,
             )
         )
 
@@ -119,10 +120,12 @@ def _reset():
         dash._pages.CONFIG.__dict__.clear()
 
     @staticmethod
-    def _get_external_assets(new_path: str, folder: Path, extension: str) -> List[str]:
-        """Returns a list of paths to assets with given `extension` in `folder`, prefixed with `new_path`.
+    def _get_external_assets(folder: Path, extension: str) -> List[str]:
+        """Returns a list of paths to assets with given `extension` in `folder`, prefixed with `STATIC_URL_PREFIX`.
 
-        e.g. with new_path="/vizro", extension="css", folder="/path/to/vizro/vizro-core/src/vizro/static",
-        we will get ["/vizro/css/accordion.css", "/vizro/css/button.css", ...].
+        e.g. with STATIC_URL_PREFIX="vizro", extension="css", folder="/path/to/vizro/vizro-core/src/vizro/static",
+        we will get ["vizro/css/accordion.css", "vizro/css/button.css", ...].
         """
-        return sorted((new_path / path.relative_to(folder)).as_posix() for path in folder.rglob(f"*.{extension}"))
+        return sorted(
+            (STATIC_URL_PREFIX / path.relative_to(folder)).as_posix() for path in folder.rglob(f"*.{extension}")
+        )