diff --git a/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/1-TSESTree-Error.shot b/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/1-TSESTree-Error.shot
index 3192c89d0208..70781ef9b372 100644
--- a/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/1-TSESTree-Error.shot
+++ b/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/1-TSESTree-Error.shot
@@ -1,4 +1,7 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`AST Fixtures > declaration > TSInterfaceDeclaration > _error_ > non-identifier-extends > TSESTree - Error`]
-NO ERROR
+TSError
+> 1 | interface F extends 1 {}
+    |                     ^ Interface declaration can only extend an identifier/qualified name with optional type arguments.
+  2 |
diff --git a/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/3-Alignment-Error.shot b/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/3-Alignment-Error.shot
index 8b8a05459c4b..a0844838800f 100644
--- a/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/3-Alignment-Error.shot
+++ b/packages/ast-spec/src/declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/snapshots/3-Alignment-Error.shot
@@ -1,4 +1,4 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`AST Fixtures > declaration > TSInterfaceDeclaration > _error_ > non-identifier-extends > Error Alignment`]
-Babel errored but TSESTree didn't
+Both errored
diff --git a/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/1-TSESTree-Error.shot b/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/1-TSESTree-Error.shot
index b9716b289515..f57a1b692cd1 100644
--- a/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/1-TSESTree-Error.shot
+++ b/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/1-TSESTree-Error.shot
@@ -1,4 +1,9 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`AST Fixtures > legacy-fixtures > errorRecovery > _error_ > interface-multiple-extends > TSESTree - Error`]
-NO ERROR
+TSError
+  1 | // TODO: This fixture might be too large, and if so should be split up.
+  2 |
+> 3 | interface foo extends bar extends baz {}
+    |                           ^^^^^^^^^^^ 'extends' clause already seen.
+  4 |
diff --git a/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/3-Alignment-Error.shot b/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/3-Alignment-Error.shot
index 8c05c9ec9327..2b5ef310d7cd 100644
--- a/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/3-Alignment-Error.shot
+++ b/packages/ast-spec/src/legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/snapshots/3-Alignment-Error.shot
@@ -1,4 +1,4 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`AST Fixtures > legacy-fixtures > errorRecovery > _error_ > interface-multiple-extends > Error Alignment`]
-Babel errored but TSESTree didn't
+Both errored
diff --git a/packages/ast-spec/tests/fixtures-with-differences-errors.shot b/packages/ast-spec/tests/fixtures-with-differences-errors.shot
index ef7f47117298..7051aa777fbb 100644
--- a/packages/ast-spec/tests/fixtures-with-differences-errors.shot
+++ b/packages/ast-spec/tests/fixtures-with-differences-errors.shot
@@ -12,7 +12,6 @@ exports[`AST Fixtures > List fixtures with Error differences`]
     "declaration/TSImportEqualsDeclaration/fixtures/_error_/import-kind/fixture.ts",
     "declaration/TSInterfaceDeclaration/fixtures/_error_/missing-extends/fixture.ts",
     "declaration/TSInterfaceDeclaration/fixtures/_error_/missing-type-param/fixture.ts",
-    "declaration/TSInterfaceDeclaration/fixtures/_error_/non-identifier-extends/fixture.ts",
     "declaration/TSTypeAliasDeclaration/fixtures/_error_/missing-type-parameter/fixture.ts",
     "declaration/VariableDeclaration/fixtures/_error_/const-destructure-no-init/fixture.ts",
     "declaration/VariableDeclaration/fixtures/_error_/const-destructure-type-no-init/fixture.ts",
@@ -45,7 +44,6 @@ exports[`AST Fixtures > List fixtures with Error differences`]
     "legacy-fixtures/errorRecovery/fixtures/_error_/empty-type-parameters/fixture.ts",
     "legacy-fixtures/errorRecovery/fixtures/_error_/index-signature-parameters/fixture.ts",
     "legacy-fixtures/errorRecovery/fixtures/_error_/interface-empty-extends/fixture.ts",
-    "legacy-fixtures/errorRecovery/fixtures/_error_/interface-multiple-extends/fixture.ts",
     "legacy-fixtures/errorRecovery/fixtures/_error_/interface-with-optional-index-signature/fixture.ts",
     "legacy-fixtures/parameter-decorators/fixtures/_error_/parameter-array-pattern-decorator/fixture.ts",
     "legacy-fixtures/parameter-decorators/fixtures/_error_/parameter-rest-element-decorator/fixture.ts",
diff --git a/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars.test.ts b/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars.test.ts
index 5ebc8d9a406b..5f40bbcdc3cc 100644
--- a/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars.test.ts
@@ -360,25 +360,6 @@ export interface Bar extends baz.test {}
       code: `
 import test from 'test';
 import baz from 'baz';
-export interface Bar extends baz().test {}
-      `,
-      errors: [
-        {
-          column: 8,
-          data: {
-            action: 'defined',
-            additional: '',
-            varName: 'test',
-          },
-          line: 2,
-          messageId: 'unusedVar',
-        },
-      ],
-    },
-    {
-      code: `
-import test from 'test';
-import baz from 'baz';
 export class Bar implements baz.test {}
       `,
       errors: [
diff --git a/packages/typescript-estree/src/convert.ts b/packages/typescript-estree/src/convert.ts
index 22c0257505a2..8f293db2af02 100644
--- a/packages/typescript-estree/src/convert.ts
+++ b/packages/typescript-estree/src/convert.ts
@@ -70,6 +70,25 @@ export interface ASTMaps {
   tsNodeToESTreeNodeMap: ParserWeakMap<TSNode, TSESTree.Node>;
 }
 
+function isPropertyAccessEntityNameExpression(
+  node: ts.Node,
+): node is ts.PropertyAccessEntityNameExpression {
+  return (
+    ts.isPropertyAccessExpression(node) &&
+    ts.isIdentifier(node.name) &&
+    isEntityNameExpression(node.expression)
+  );
+}
+
+function isEntityNameExpression(
+  node: ts.Node,
+): node is ts.EntityNameExpression {
+  return (
+    node.kind === SyntaxKind.Identifier ||
+    isPropertyAccessEntityNameExpression(node)
+  );
+}
+
 export class Converter {
   private allowPattern = false;
   private readonly ast: ts.SourceFile;
@@ -3024,6 +3043,7 @@ export class Converter {
         const interfaceHeritageClauses = node.heritageClauses ?? [];
         const interfaceExtends: TSESTree.TSInterfaceHeritage[] = [];
 
+        let seenExtendsClause = false;
         for (const heritageClause of interfaceHeritageClauses) {
           if (heritageClause.token !== SyntaxKind.ExtendsKeyword) {
             this.#throwError(
@@ -3033,8 +3053,21 @@ export class Converter {
                 : 'Unexpected token.',
             );
           }
+          if (seenExtendsClause) {
+            this.#throwError(heritageClause, "'extends' clause already seen.");
+          }
+          seenExtendsClause = true;
 
           for (const heritageType of heritageClause.types) {
+            if (
+              !isEntityNameExpression(heritageType.expression) ||
+              ts.isOptionalChain(heritageType.expression)
+            ) {
+              this.#throwError(
+                heritageType,
+                'Interface declaration can only extend an identifier/qualified name with optional type arguments.',
+              );
+            }
             interfaceExtends.push(
               this.convertChild(
                 heritageType,