diff --git a/.changeset/wise-trams-like.md b/.changeset/wise-trams-like.md
new file mode 100644
index 00000000..49eef37d
--- /dev/null
+++ b/.changeset/wise-trams-like.md
@@ -0,0 +1,5 @@
+---
+'@hono/otel': patch
+---
+
+Add explicit `MiddlewareHandler` return type
diff --git a/packages/otel/src/index.ts b/packages/otel/src/index.ts
index e359199d..7fa0d67d 100644
--- a/packages/otel/src/index.ts
+++ b/packages/otel/src/index.ts
@@ -8,7 +8,7 @@ import {
   ATTR_URL_FULL,
   ATTR_HTTP_ROUTE,
 } from '@opentelemetry/semantic-conventions'
-import type { Env, Input } from 'hono'
+import type { MiddlewareHandler } from 'hono'
 import { createMiddleware } from 'hono/factory'
 import metadata from '../package.json' with { type: 'json' }
 
@@ -24,11 +24,9 @@ export type OtelOptions =
       augmentSpan: true
     }
 
-export const otel = <E extends Env = any, P extends string = any, I extends Input = {}>(
-  options: OtelOptions = {}
-) => {
+export const otel = (options: OtelOptions = {}): MiddlewareHandler => {
   if (options.augmentSpan) {
-    return createMiddleware<E, P, I>(async (c, next) => {
+    return createMiddleware(async (c, next) => {
       const result = await next()
       const span = trace.getActiveSpan()
       if (span != null) {
@@ -41,7 +39,7 @@ export const otel = <E extends Env = any, P extends string = any, I extends Inpu
   }
   const tracerProvider = options.tracerProvider ?? trace.getTracerProvider()
   const tracer = tracerProvider.getTracer(PACKAGE_NAME, PACKAGE_VERSION)
-  return createMiddleware<E, P, I>(async (c, next) => {
+  return createMiddleware(async (c, next) => {
     // Handle propagation of trace context from a request using the W3C Trace Context format
     let activeContext = context.active()
     if (c.req.header('traceparent')) {
diff --git a/packages/otel/tsconfig.build.json b/packages/otel/tsconfig.build.json
index 66b0baa9..b8855cf8 100644
--- a/packages/otel/tsconfig.build.json
+++ b/packages/otel/tsconfig.build.json
@@ -4,7 +4,8 @@
     "rootDir": "src",
     "outDir": "dist",
     "tsBuildInfoFile": "dist/tsconfig.build.tsbuildinfo",
-    "emitDeclarationOnly": false
+    "emitDeclarationOnly": false,
+    "isolatedDeclarations": true
   },
   "include": ["package.json", "src/**/*.ts"],
   "exclude": ["**/*.test.ts"],