diff --git a/.changeset/brave-paws-cheer.md b/.changeset/brave-paws-cheer.md
new file mode 100644
index 000000000000..a72752892ca4
--- /dev/null
+++ b/.changeset/brave-paws-cheer.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': minor
+---
+
+feat: add warning for mistyped route filenames
diff --git a/packages/kit/src/core/sync/create_manifest_data/index.js b/packages/kit/src/core/sync/create_manifest_data/index.js
index 06426dad5655..d5f8dd1cde6a 100644
--- a/packages/kit/src/core/sync/create_manifest_data/index.js
+++ b/packages/kit/src/core/sync/create_manifest_data/index.js
@@ -1,5 +1,6 @@
 import fs from 'node:fs';
 import path from 'node:path';
+import colors from 'kleur';
 import mime from 'mime';
 import { list_files, runtime_directory } from '../../utils.js';
 import { posixify } from '../../../utils/filesystem.js';
@@ -201,8 +202,31 @@ function create_routes_and_nodes(cwd, config, fallback) {
 			// process files first
 			for (const file of files) {
 				if (file.is_dir) continue;
-				if (!file.name.startsWith('+')) continue;
-				if (!valid_extensions.find((ext) => file.name.endsWith(ext))) continue;
+
+				const ext = valid_extensions.find((ext) => file.name.endsWith(ext));
+				if (!ext) continue;
+
+				if (!file.name.startsWith('+')) {
+					const name = file.name.slice(0, -ext.length);
+					// check if it is a valid route filename but missing the + prefix
+					const typo =
+						/^(?:(page(?:@(.*))?)|(layout(?:@(.*))?)|(error))$/.test(name) ||
+						/^(?:(server)|(page(?:(@[a-zA-Z0-9_-]*))?(\.server)?)|(layout(?:(@[a-zA-Z0-9_-]*))?(\.server)?))$/.test(
+							name
+						);
+					if (typo) {
+						console.log(
+							colors
+								.bold()
+								.yellow(
+									`Missing route file prefix. Did you mean +${file.name}?` +
+										` at ${path.join(dir, file.name)}`
+								)
+						);
+					}
+
+					continue;
+				}
 
 				if (file.name.endsWith('.d.ts')) {
 					let name = file.name.slice(0, -5);
diff --git a/packages/kit/src/core/sync/write_client_manifest.js b/packages/kit/src/core/sync/write_client_manifest.js
index 623dbf468f0f..7e65baf2caf4 100644
--- a/packages/kit/src/core/sync/write_client_manifest.js
+++ b/packages/kit/src/core/sync/write_client_manifest.js
@@ -1,6 +1,8 @@
+import path from 'node:path';
 import { relative_path, resolve_entry } from '../../utils/filesystem.js';
 import { s } from '../../utils/misc.js';
 import { dedent, write_if_changed } from './utils.js';
+import colors from 'kleur';
 
 /**
  * Writes the client manifest to disk. The manifest is used to power the router. It contains the
@@ -108,6 +110,18 @@ export function write_client_manifest(kit, manifest_data, output, metadata) {
 
 	const hooks_file = resolve_entry(kit.files.hooks.client);
 
+	const typo = resolve_entry('src/+hooks.client');
+	if (typo) {
+		console.log(
+			colors
+				.bold()
+				.yellow(
+					`Unexpected + prefix. Did you mean ${typo.split('/').at(-1)?.slice(1)}?` +
+						` at ${path.resolve(typo)}`
+				)
+		);
+	}
+
 	write_if_changed(
 		`${output}/app.js`,
 		dedent`
diff --git a/packages/kit/src/core/sync/write_server.js b/packages/kit/src/core/sync/write_server.js
index 71ff99aac3c5..976417f504f7 100644
--- a/packages/kit/src/core/sync/write_server.js
+++ b/packages/kit/src/core/sync/write_server.js
@@ -1,4 +1,3 @@
-import fs from 'node:fs';
 import path from 'node:path';
 import { hash } from '../../runtime/hash.js';
 import { posixify, resolve_entry } from '../../utils/filesystem.js';
@@ -6,6 +5,7 @@ import { s } from '../../utils/misc.js';
 import { load_error_page, load_template } from '../config/index.js';
 import { runtime_directory } from '../utils.js';
 import { write_if_changed } from './utils.js';
+import colors from 'kleur';
 
 /**
  * @param {{
@@ -76,8 +76,19 @@ export { set_assets, set_building, set_private_env, set_public_env };
  * @param {string} output
  */
 export function write_server(config, output) {
-	// TODO the casting shouldn't be necessary — investigate
-	const hooks_file = /** @type {string} */ (resolve_entry(config.kit.files.hooks.server));
+	const hooks_file = resolve_entry(config.kit.files.hooks.server);
+
+	const typo = resolve_entry('src/+hooks.server');
+	if (typo) {
+		console.log(
+			colors
+				.bold()
+				.yellow(
+					`Unexpected + prefix. Did you mean ${typo.split('/').at(-1)?.slice(1)}?` +
+						` at ${path.resolve(typo)}`
+				)
+		);
+	}
 
 	/** @param {string} file */
 	function relative(file) {
@@ -88,7 +99,7 @@ export function write_server(config, output) {
 		`${output}/server/internal.js`,
 		server_template({
 			config,
-			hooks: fs.existsSync(hooks_file) ? relative(hooks_file) : null,
+			hooks: hooks_file ? relative(hooks_file) : null,
 			has_service_worker:
 				config.kit.serviceWorker.register && !!resolve_entry(config.kit.files.serviceWorker),
 			runtime_directory: relative(runtime_directory),