diff --git a/crates/oxc_parser/src/diagnostics.rs b/crates/oxc_parser/src/diagnostics.rs
index 178427b10ab20..87f65d51aca24 100644
--- a/crates/oxc_parser/src/diagnostics.rs
+++ b/crates/oxc_parser/src/diagnostics.rs
@@ -1121,6 +1121,11 @@ pub fn parameter_modifiers_in_ts(
         .with_allowed_modifier_help(allowed)
 }
 
+#[cold]
+pub fn implements_clause_in_ts(span: Span) -> OxcDiagnostic {
+    ts_error("8005", "'implements' clauses can only be used in TypeScript files.").with_label(span)
+}
+
 #[cold]
 pub fn implementation_in_ambient(span: Span) -> OxcDiagnostic {
     ts_error("1183", "An implementation cannot be declared in ambient contexts.").with_label(span)
diff --git a/crates/oxc_parser/src/js/class.rs b/crates/oxc_parser/src/js/class.rs
index 33d4b4600d3fa..ad96b967ad983 100644
--- a/crates/oxc_parser/src/js/class.rs
+++ b/crates/oxc_parser/src/js/class.rs
@@ -146,6 +146,9 @@ impl<'a, C: Config> ParserImpl<'a, C> {
                         ));
                     }
                     let implements_kw_span = self.cur_token().span();
+                    if !self.is_ts {
+                        self.error(diagnostics::implements_clause_in_ts(implements_kw_span));
+                    }
                     if let Some((_, implements)) = implements.as_mut() {
                         implements.extend(self.parse_ts_implements_clause());
                     } else {
diff --git a/tasks/coverage/snapshots/parser_typescript.snap b/tasks/coverage/snapshots/parser_typescript.snap
index c8b49013ca6ca..12853113038e9 100644
--- a/tasks/coverage/snapshots/parser_typescript.snap
+++ b/tasks/coverage/snapshots/parser_typescript.snap
@@ -3,7 +3,7 @@ commit: 34725489
 parser_typescript Summary:
 AST Parsed     : 9831/9834 (99.97%)
 Positive Passed: 9820/9834 (99.86%)
-Negative Passed: 1527/2578 (59.23%)
+Negative Passed: 1528/2578 (59.27%)
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/FunctionDeclaration3.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/FunctionDeclaration4.ts
@@ -530,8 +530,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/jsFileCompil
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/jsFileCompilationDuplicateFunctionImplementationFileOrderReversed.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/jsFileCompilationHeritageClauseSyntaxOfClass.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/jsFileCompilationOptionalClassElementSyntaxOfClass.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/jsFileCompilationPublicMethodSyntaxOfClass.ts
@@ -7370,6 +7368,12 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ╰────
   help: Add a function body (`{}`).
 
+  × TS(8005): 'implements' clauses can only be used in TypeScript files.
+   ╭─[typescript/tests/cases/compiler/jsFileCompilationHeritageClauseSyntaxOfClass.ts:1:9]
+ 1 │ class C implements D { }
+   ·         ──────────
+   ╰────
+
   × TS(8002): 'import ... =' can only be used in TypeScript files.
    ╭─[typescript/tests/cases/compiler/jsFileCompilationImportEqualsSyntax.ts:1:1]
  1 │ import a = b;