diff --git a/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/fixture.ts b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/fixture.ts
new file mode 100644
index 00000000000..698850476ff
--- /dev/null
+++ b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/fixture.ts
@@ -0,0 +1,3 @@
+switch (true) {
+	default: default:
+}
diff --git a/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/1-TSESTree-Error.shot b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/1-TSESTree-Error.shot
new file mode 100644
index 00000000000..ee04bea45a4
--- /dev/null
+++ b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/1-TSESTree-Error.shot
@@ -0,0 +1,12 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`AST Fixtures statement SwitchStatement _error_ multiple-default-cases TSESTree - Error 1`] = `
+"TSError
+> 1 | switch (true) {
+    | ^^^^^^^^^^^^^^^
+> 2 | 	default: default:
+    | ^^^^^^^^^^^^^^^^^^
+> 3 | }
+    | ^^ A 'default' clause cannot appear more than once in a 'switch' statement.
+  4 |"
+`;
diff --git a/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/2-Babel-Error.shot b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/2-Babel-Error.shot
new file mode 100644
index 00000000000..36271efa74a
--- /dev/null
+++ b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/2-Babel-Error.shot
@@ -0,0 +1,3 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`AST Fixtures statement SwitchStatement _error_ multiple-default-cases Babel - Error 1`] = `[SyntaxError: Multiple default clauses. (2:10)]`;
diff --git a/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/3-Alignment-Error.shot b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/3-Alignment-Error.shot
new file mode 100644
index 00000000000..37a7c334d63
--- /dev/null
+++ b/packages/ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/3-Alignment-Error.shot
@@ -0,0 +1,3 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`AST Fixtures statement SwitchStatement _error_ multiple-default-cases Error Alignment 1`] = `"Both errored"`;
diff --git a/packages/typescript-estree/src/convert.ts b/packages/typescript-estree/src/convert.ts
index 13882d67c9c..7f248e49737 100644
--- a/packages/typescript-estree/src/convert.ts
+++ b/packages/typescript-estree/src/convert.ts
@@ -844,6 +844,17 @@ export class Converter {
         });
 
       case SyntaxKind.SwitchStatement:
+        if (
+          node.caseBlock.clauses.filter(
+            switchCase => switchCase.kind === SyntaxKind.DefaultClause,
+          ).length > 1
+        ) {
+          this.#throwError(
+            node,
+            "A 'default' clause cannot appear more than once in a 'switch' statement.",
+          );
+        }
+
         return this.createNode<TSESTree.SwitchStatement>(node, {
           type: AST_NODE_TYPES.SwitchStatement,
           discriminant: this.convertChild(node.expression),