diff --git a/.changeset/dirty-dolls-pay.md b/.changeset/dirty-dolls-pay.md
new file mode 100644
index 0000000000..fb08aadea0
--- /dev/null
+++ b/.changeset/dirty-dolls-pay.md
@@ -0,0 +1,5 @@
+---
+"@react-router/dev": patch
+---
+
+Allow `.mts` and `.mjs` extensions for route config file
diff --git a/packages/react-router-dev/config/config.ts b/packages/react-router-dev/config/config.ts
index da84bcd3f0..0b4a627573 100644
--- a/packages/react-router-dev/config/config.ts
+++ b/packages/react-router-dev/config/config.ts
@@ -914,7 +914,7 @@ function omitRoutes(
   };
 }
 
-const entryExts = [".js", ".jsx", ".ts", ".tsx"];
+const entryExts = [".js", ".jsx", ".ts", ".tsx", ".mjs", ".mts"];
 
 function isEntryFile(entryBasename: string, filename: string) {
   return entryExts.some((ext) => filename === `${entryBasename}${ext}`);