diff --git a/.changeset/chilled-drinks-itch.md b/.changeset/chilled-drinks-itch.md
new file mode 100644
index 000000000000..d08fbf48603b
--- /dev/null
+++ b/.changeset/chilled-drinks-itch.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: remove unused SSR CSS assets
diff --git a/packages/kit/src/exports/vite/index.js b/packages/kit/src/exports/vite/index.js
index 94f242a1e468..ff61a63af05a 100644
--- a/packages/kit/src/exports/vite/index.js
+++ b/packages/kit/src/exports/vite/index.js
@@ -720,10 +720,20 @@ function kit({ svelte_config }) {
 					})
 				);
 
-				copy(
-					`${out}/server/${kit.appDir}/immutable/assets`,
-					`${out}/client/${kit.appDir}/immutable/assets`
-				);
+				// don't copy unused CSS generated by Vite's build.ssrEmitAssets option
+				const server_css = Object.values(server_manifest)
+					.filter((entry) => entry.css)
+					.map((entry) => entry.css)
+					.flat();
+
+				const assets_path = `${kit.appDir}/immutable/assets`;
+
+				copy(`${out}/server/${assets_path}`, `${out}/client/${assets_path}`, {
+					filter: (basename) => {
+						const filepath = `${assets_path}/${basename}`;
+						return !server_css.includes(filepath);
+					}
+				});
 
 				/** @type {import('vite').Manifest} */
 				const client_manifest = JSON.parse(read(`${out}/client/${vite_config.build.manifest}`));