diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 5ccd346a93b4f..4362c23ce4058 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -462,6 +462,8 @@ Bug Fixes in This Version
 - Fixed a crash when ``#embed`` appears as a part of a failed constant
   evaluation. The crashes were happening during diagnostics emission due to
   unimplemented statement printer. (#GH132641)
+- Clang now correctly diagnoses the deleted/defaulted redeclaration of defined
+  friend functions. (#GH135680)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Parse/ParseCXXInlineMethods.cpp b/clang/lib/Parse/ParseCXXInlineMethods.cpp
index b1064eb02b907..d28353486c493 100644
--- a/clang/lib/Parse/ParseCXXInlineMethods.cpp
+++ b/clang/lib/Parse/ParseCXXInlineMethods.cpp
@@ -142,6 +142,14 @@ NamedDecl *Parser::ParseCXXInlineMethodDef(
       SkipUntil(tok::semi);
     }
 
+    if (FunctionDecl *FD =
+            dyn_cast_if_present<FunctionDecl>(FnD->getPreviousDecl())) {
+      if (isa<CXXRecordDecl>(FD->getLexicalDeclContext()) ||
+          Actions.getDefaultedFunctionKind(FD).asComparison() ==
+              Sema::DefaultedComparisonKind::None)
+        Actions.CheckForFunctionRedefinition(FnD->getAsFunction(), FD);
+    }
+
     return FnD;
   }
 
diff --git a/clang/test/SemaCXX/cxx2c-delete-with-message.cpp b/clang/test/SemaCXX/cxx2c-delete-with-message.cpp
index 5609da18c05aa..78524c50e615c 100644
--- a/clang/test/SemaCXX/cxx2c-delete-with-message.cpp
+++ b/clang/test/SemaCXX/cxx2c-delete-with-message.cpp
@@ -273,31 +273,34 @@ void operators() {
 };
 
 namespace gh135506 {
-struct a {
-  // FIXME: We currently don't diagnose these invalid redeclarations if the
-  // second declaration is defaulted or deleted. This probably needs to be
-  // handled in ParseCXXInlineMethodDef() after parsing the defaulted/deleted
-  // body.
-  friend consteval int f() { return 3; }
-  friend consteval int f() = delete("foo");
-
-  friend consteval int g() { return 3; }
-  friend consteval int g() = delete;
-
-  friend int h() { return 3; }
-  friend int h() = delete;
-
-  friend consteval int i() = delete; // expected-note {{previous definition is here}}
-  friend consteval int i() { return 3; } // expected-error {{redefinition of 'i'}}
+struct s1 {
+  friend consteval int a() { return 3; }    // expected-note {{previous definition is here}}
+  friend consteval int a() = delete("foo"); // expected-error {{redefinition of 'a'}}
+
+  friend consteval int b() { return 3; } // expected-note {{previous definition is here}}
+  friend consteval int b() = delete;     // expected-error {{redefinition of 'b'}}
+
+  friend int c() { return 3; } // expected-note {{previous definition is here}}
+  friend int c() = delete;     // expected-error {{redefinition of 'c'}}
+
+  friend consteval int d() = delete;     // expected-note {{previous definition is here}}
+  friend consteval int d() { return 3; } // expected-error {{redefinition of 'd'}}
 };
 
-struct b {
-  friend consteval bool operator==(b, b) { return true; } // expected-note {{previous declaration is here}}
-  friend consteval bool operator==(b, b) = default; // expected-error {{defaulting this equality comparison operator is not allowed because it was already declared outside the class}}
+struct s2 {
+  friend consteval bool operator==(s2, s2) { return true; } // expected-note {{previous definition is here}}
+  friend consteval bool operator==(s2, s2) = default;       // expected-error {{redefinition of 'operator=='}}
 };
 
-struct c {
-  friend consteval bool operator==(c, c) = default; // expected-note {{previous definition is here}}
-  friend consteval bool operator==(c, c) { return true; } // expected-error {{redefinition of 'operator=='}}
+struct s3 {
+  friend consteval bool operator==(s3, s3) = default;       // expected-note {{previous definition is here}}
+  friend consteval bool operator==(s3, s3) { return true; } // expected-error {{redefinition of 'operator=='}}
 };
+
+void e() {}                              // expected-note {{previous definition is here}}
+struct s4 { friend void e() = delete; }; // expected-error {{redefinition of 'e'}}
+
+struct s5 { friend void f() {} };         // expected-note {{previous definition is here}}
+struct s6 { friend void f() = delete; };  // expected-error {{redefinition of 'f'}}
+
 }