diff --git a/Sources/SwiftJavaMacros/ImplementsJavaMacro.swift b/Sources/SwiftJavaMacros/ImplementsJavaMacro.swift
index b3057ae4..91cd3211 100644
--- a/Sources/SwiftJavaMacros/ImplementsJavaMacro.swift
+++ b/Sources/SwiftJavaMacros/ImplementsJavaMacro.swift
@@ -16,10 +16,39 @@ import SwiftSyntax
 import SwiftSyntaxBuilder
 import SwiftSyntaxMacros
 
-enum JavaImplementationMacro {}
+package enum JavaImplementationMacro {}
+
+// JNI identifier escaping per the JNI specification:
+// https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/design.html#resolving_native_method_names
+extension String {
+  /// Returns the string with characters escaped according to JNI symbol naming rules.
+  /// - `_` → `_1`
+  /// - `.` and `/` → `_` (package/class separator)
+  /// - `;` → `_2`
+  /// - `[` → `_3`
+  /// - Non-ASCII → `_0XXXX` (UTF-16 hex)
+  var escapedJNIIdentifier: String {
+    self.compactMap { ch -> String in
+      switch ch {
+      case "_": return "_1"
+      case "/": return "_"
+      case ";": return "_2"
+      case "[": return "_3"
+      default:
+        if ch.isASCII && (ch.isLetter || ch.isNumber) {
+          return String(ch)
+        } else if let utf16 = ch.utf16.first {
+          return "_0\(String(format: "%04x", utf16))"
+        } else {
+          fatalError("Invalid JNI character: \(ch)")
+        }
+      }
+    }.joined()
+  }
+}
 
 extension JavaImplementationMacro: PeerMacro {
-  static func expansion(
+  package static func expansion(
     of node: AttributeSyntax,
     providingPeersOf declaration: some DeclSyntaxProtocol,
     in context: some MacroExpansionContext
@@ -112,7 +141,8 @@ extension JavaImplementationMacro: PeerMacro {
         } ?? ""
 
       let swiftName = memberFunc.name.text
-      let cName = "Java_" + className.replacingOccurrences(of: ".", with: "_") + "_" + swiftName
+      let escapedClassName = className.split(separator: ".").map { String($0).escapedJNIIdentifier }.joined(separator: "_")
+      let cName = "Java_" + escapedClassName + "_" + swiftName.escapedJNIIdentifier
       let innerBody: CodeBlockItemListSyntax
       let isThrowing = memberFunc.signature.effectSpecifiers?.throwsClause != nil
       let tryClause: String = isThrowing ? "try " : ""
diff --git a/Tests/SwiftJavaMacrosTests/JavaImplementationMacroTests.swift b/Tests/SwiftJavaMacrosTests/JavaImplementationMacroTests.swift
new file mode 100644
index 00000000..aaea2568
--- /dev/null
+++ b/Tests/SwiftJavaMacrosTests/JavaImplementationMacroTests.swift
@@ -0,0 +1,190 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftJavaMacros
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import SwiftSyntaxMacros
+import SwiftSyntaxMacrosTestSupport
+import XCTest
+
+class JavaImplementationMacroTests: XCTestCase {
+  static let javaImplementationMacros: [String: any Macro.Type] = [
+    "JavaImplementation": JavaImplementationMacro.self,
+    "JavaMethod": JavaMethodMacro.self,
+  ]
+
+  func testJNIIdentifierEscaping() throws {
+    assertMacroExpansion(
+      """
+      @JavaImplementation("org.swift.example.Hello_World")
+      extension HelloWorld {
+        @JavaMethod
+        func test_method() -> Int32 {
+          return 42
+        }
+      }
+      """,
+      expandedSource: """
+
+        extension HelloWorld {
+          func test_method() -> Int32 {
+              return 42
+          }
+        }
+
+        @_cdecl("Java_org_swift_example_Hello_1World_test_1method")
+        func __macro_local_11test_methodfMu_(environment: UnsafeMutablePointer<JNIEnv?>!, thisObj: jobject) -> Int32.JNIType {
+          let obj = HelloWorld(javaThis: thisObj, environment: environment!)
+          return obj.test_method()
+          .getJNIValue(in: environment)
+        }
+        """,
+      macros: Self.javaImplementationMacros
+    )
+  }
+
+  func testJNIIdentifierEscapingWithDots() throws {
+    assertMacroExpansion(
+      """
+      @JavaImplementation("com.example.test.MyClass")
+      extension MyClass {
+        @JavaMethod
+        func simpleMethod() -> Int32 {
+          return 1
+        }
+      }
+      """,
+      expandedSource: """
+
+        extension MyClass {
+          func simpleMethod() -> Int32 {
+              return 1
+          }
+        }
+
+        @_cdecl("Java_com_example_test_MyClass_simpleMethod")
+        func __macro_local_12simpleMethodfMu_(environment: UnsafeMutablePointer<JNIEnv?>!, thisObj: jobject) -> Int32.JNIType {
+          let obj = MyClass(javaThis: thisObj, environment: environment!)
+          return obj.simpleMethod()
+          .getJNIValue(in: environment)
+        }
+        """,
+      macros: Self.javaImplementationMacros
+    )
+  }
+
+  func testJNIIdentifierEscapingStaticMethod() throws {
+    assertMacroExpansion(
+      """
+      @JavaImplementation("org.example.Utils")
+      extension Utils {
+        @JavaMethod
+        static func static_helper(environment: JNIEnvironment) -> String {
+          return "hello"
+        }
+      }
+      """,
+      expandedSource: """
+
+        extension Utils {
+          static func static_helper(environment: JNIEnvironment) -> String {
+              return "hello"
+          }
+        }
+
+        @_cdecl("Java_org_example_Utils_static_1helper")
+        func __macro_local_13static_helperfMu_(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass) -> String.JNIType {
+          return Utils.static_helper(environment: environment)
+          .getJNIValue(in: environment)
+        }
+        """,
+      macros: Self.javaImplementationMacros
+    )
+  }
+
+  func testJNIIdentifierEscapingMultipleMethods() throws {
+    assertMacroExpansion(
+      """
+      @JavaImplementation("test.Class_With_Underscores")
+      extension ClassWithUnderscores {
+        @JavaMethod
+        func method_one() -> Int32 {
+          return 1
+        }
+
+        @JavaMethod
+        func method_two() -> Int32 {
+          return 2
+        }
+      }
+      """,
+      expandedSource: """
+
+        extension ClassWithUnderscores {
+          func method_one() -> Int32 {
+              return 1
+          }
+          func method_two() -> Int32 {
+              return 2
+          }
+        }
+
+        @_cdecl("Java_test_Class_1With_1Underscores_method_1one")
+        func __macro_local_10method_onefMu_(environment: UnsafeMutablePointer<JNIEnv?>!, thisObj: jobject) -> Int32.JNIType {
+          let obj = ClassWithUnderscores(javaThis: thisObj, environment: environment!)
+          return obj.method_one()
+          .getJNIValue(in: environment)
+        }
+
+        @_cdecl("Java_test_Class_1With_1Underscores_method_1two")
+        func __macro_local_10method_twofMu_(environment: UnsafeMutablePointer<JNIEnv?>!, thisObj: jobject) -> Int32.JNIType {
+          let obj = ClassWithUnderscores(javaThis: thisObj, environment: environment!)
+          return obj.method_two()
+          .getJNIValue(in: environment)
+        }
+        """,
+      macros: Self.javaImplementationMacros
+    )
+  }
+
+  func testJNIIdentifierEscapingVoidReturn() throws {
+    assertMacroExpansion(
+      """
+      @JavaImplementation("org.example.Processor")
+      extension Processor {
+        @JavaMethod
+        func process_data() {
+          // do nothing
+        }
+      }
+      """,
+      expandedSource: """
+
+        extension Processor {
+          func process_data() {
+            // do nothing
+          }
+        }
+
+        @_cdecl("Java_org_example_Processor_process_1data")
+        func __macro_local_12process_datafMu_(environment: UnsafeMutablePointer<JNIEnv?>!, thisObj: jobject) {
+          let obj = Processor(javaThis: thisObj, environment: environment!)
+          return obj.process_data()
+        }
+        """,
+      macros: Self.javaImplementationMacros
+    )
+  }
+}