diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index aa677c911b874..e823695093cc0 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -846,7 +846,12 @@ namespace ts {
 
             const location = moveRangePastDecorators(node);
             const classAlias = getClassAliasIfNeeded(node);
-            const declName = factory.getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true);
+
+            // When we transform to ES5/3 this will be moved inside an IIFE and should reference the name
+            // without any block-scoped variable collision handling
+            const declName = languageVersion <= ScriptTarget.ES2015 ?
+                factory.getInternalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true) :
+                factory.getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true);
 
             //  ... = class ${name} ${heritageClauses} {
             //      ${members}
@@ -1256,7 +1261,12 @@ namespace ts {
             }
 
             const classAlias = classAliases && classAliases[getOriginalNodeId(node)];
-            const localName = factory.getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true);
+
+            // When we transform to ES5/3 this will be moved inside an IIFE and should reference the name
+            // without any block-scoped variable collision handling
+            const localName = languageVersion <= ScriptTarget.ES2015 ?
+                factory.getInternalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true) :
+                factory.getLocalName(node, /*allowComments*/ false, /*allowSourceMaps*/ true);
             const decorate = emitHelpers().createDecorateHelper(decoratorExpressions, localName);
             const expression = factory.createAssignment(localName, classAlias ? factory.createAssignment(classAlias, decorate) : decorate);
             setEmitFlags(expression, EmitFlags.NoComments);
diff --git a/tests/baselines/reference/decoratedBlockScopedClass1.js b/tests/baselines/reference/decoratedBlockScopedClass1.js
new file mode 100644
index 0000000000000..dc2b92da3b93d
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass1.js
@@ -0,0 +1,38 @@
+//// [a.ts]
+function decorator() {
+    return (target: new (...args: any[]) => any) => {}
+}
+
+@decorator()
+class Foo {
+    public static func(): Foo {
+        return new Foo();
+    }
+}
+Foo.func();
+
+
+//// [a.js]
+var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
+    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
+    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+    return c > 3 && r && Object.defineProperty(target, key, r), r;
+};
+function decorator() {
+    return function (target) { };
+}
+var Foo = /** @class */ (function () {
+    function Foo() {
+    }
+    Foo_1 = Foo;
+    Foo.func = function () {
+        return new Foo_1();
+    };
+    var Foo_1;
+    Foo = Foo_1 = __decorate([
+        decorator()
+    ], Foo);
+    return Foo;
+}());
+Foo.func();
diff --git a/tests/baselines/reference/decoratedBlockScopedClass1.symbols b/tests/baselines/reference/decoratedBlockScopedClass1.symbols
new file mode 100644
index 0000000000000..2d90c8fe77a54
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass1.symbols
@@ -0,0 +1,28 @@
+=== tests/cases/conformance/decorators/class/a.ts ===
+function decorator() {
+>decorator : Symbol(decorator, Decl(a.ts, 0, 0))
+
+    return (target: new (...args: any[]) => any) => {}
+>target : Symbol(target, Decl(a.ts, 1, 12))
+>args : Symbol(args, Decl(a.ts, 1, 25))
+}
+
+@decorator()
+>decorator : Symbol(decorator, Decl(a.ts, 0, 0))
+
+class Foo {
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+
+    public static func(): Foo {
+>func : Symbol(Foo.func, Decl(a.ts, 5, 11))
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+
+        return new Foo();
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+    }
+}
+Foo.func();
+>Foo.func : Symbol(Foo.func, Decl(a.ts, 5, 11))
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+>func : Symbol(Foo.func, Decl(a.ts, 5, 11))
+
diff --git a/tests/baselines/reference/decoratedBlockScopedClass1.types b/tests/baselines/reference/decoratedBlockScopedClass1.types
new file mode 100644
index 0000000000000..f51de5f6f0145
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass1.types
@@ -0,0 +1,31 @@
+=== tests/cases/conformance/decorators/class/a.ts ===
+function decorator() {
+>decorator : () => (target: new (...args: any[]) => any) => void
+
+    return (target: new (...args: any[]) => any) => {}
+>(target: new (...args: any[]) => any) => {} : (target: new (...args: any[]) => any) => void
+>target : new (...args: any[]) => any
+>args : any[]
+}
+
+@decorator()
+>decorator() : (target: new (...args: any[]) => any) => void
+>decorator : () => (target: new (...args: any[]) => any) => void
+
+class Foo {
+>Foo : Foo
+
+    public static func(): Foo {
+>func : () => Foo
+
+        return new Foo();
+>new Foo() : Foo
+>Foo : typeof Foo
+    }
+}
+Foo.func();
+>Foo.func() : Foo
+>Foo.func : () => Foo
+>Foo : typeof Foo
+>func : () => Foo
+
diff --git a/tests/baselines/reference/decoratedBlockScopedClass2.js b/tests/baselines/reference/decoratedBlockScopedClass2.js
new file mode 100644
index 0000000000000..9b23dfc7ec434
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass2.js
@@ -0,0 +1,44 @@
+//// [a.ts]
+function decorator() {
+    return (target: new (...args: any[]) => any) => {}
+}
+
+try {
+    @decorator()
+    class Foo {
+        public static func(): Foo {
+            return new Foo();
+        }
+    }
+    Foo.func();
+}
+catch (e) {}
+
+
+//// [a.js]
+var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
+    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
+    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+    return c > 3 && r && Object.defineProperty(target, key, r), r;
+};
+function decorator() {
+    return function (target) { };
+}
+try {
+    var Foo_1 = /** @class */ (function () {
+        function Foo() {
+        }
+        Foo_2 = Foo;
+        Foo.func = function () {
+            return new Foo_2();
+        };
+        var Foo_2;
+        Foo = Foo_2 = __decorate([
+            decorator()
+        ], Foo);
+        return Foo;
+    }());
+    Foo_1.func();
+}
+catch (e) { }
diff --git a/tests/baselines/reference/decoratedBlockScopedClass2.symbols b/tests/baselines/reference/decoratedBlockScopedClass2.symbols
new file mode 100644
index 0000000000000..b64af9e490b4d
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass2.symbols
@@ -0,0 +1,32 @@
+=== tests/cases/conformance/decorators/class/a.ts ===
+function decorator() {
+>decorator : Symbol(decorator, Decl(a.ts, 0, 0))
+
+    return (target: new (...args: any[]) => any) => {}
+>target : Symbol(target, Decl(a.ts, 1, 12))
+>args : Symbol(args, Decl(a.ts, 1, 25))
+}
+
+try {
+    @decorator()
+>decorator : Symbol(decorator, Decl(a.ts, 0, 0))
+
+    class Foo {
+>Foo : Symbol(Foo, Decl(a.ts, 4, 5))
+
+        public static func(): Foo {
+>func : Symbol(Foo.func, Decl(a.ts, 6, 15))
+>Foo : Symbol(Foo, Decl(a.ts, 4, 5))
+
+            return new Foo();
+>Foo : Symbol(Foo, Decl(a.ts, 4, 5))
+        }
+    }
+    Foo.func();
+>Foo.func : Symbol(Foo.func, Decl(a.ts, 6, 15))
+>Foo : Symbol(Foo, Decl(a.ts, 4, 5))
+>func : Symbol(Foo.func, Decl(a.ts, 6, 15))
+}
+catch (e) {}
+>e : Symbol(e, Decl(a.ts, 13, 7))
+
diff --git a/tests/baselines/reference/decoratedBlockScopedClass2.types b/tests/baselines/reference/decoratedBlockScopedClass2.types
new file mode 100644
index 0000000000000..9ce4353b0bc8e
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass2.types
@@ -0,0 +1,35 @@
+=== tests/cases/conformance/decorators/class/a.ts ===
+function decorator() {
+>decorator : () => (target: new (...args: any[]) => any) => void
+
+    return (target: new (...args: any[]) => any) => {}
+>(target: new (...args: any[]) => any) => {} : (target: new (...args: any[]) => any) => void
+>target : new (...args: any[]) => any
+>args : any[]
+}
+
+try {
+    @decorator()
+>decorator() : (target: new (...args: any[]) => any) => void
+>decorator : () => (target: new (...args: any[]) => any) => void
+
+    class Foo {
+>Foo : Foo
+
+        public static func(): Foo {
+>func : () => Foo
+
+            return new Foo();
+>new Foo() : Foo
+>Foo : typeof Foo
+        }
+    }
+    Foo.func();
+>Foo.func() : Foo
+>Foo.func : () => Foo
+>Foo : typeof Foo
+>func : () => Foo
+}
+catch (e) {}
+>e : any
+
diff --git a/tests/baselines/reference/decoratedBlockScopedClass3.js b/tests/baselines/reference/decoratedBlockScopedClass3.js
new file mode 100644
index 0000000000000..c0ff1ceb85394
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass3.js
@@ -0,0 +1,66 @@
+//// [a.ts]
+function decorator() {
+    return (target: new (...args: any[]) => any) => {}
+}
+
+@decorator()
+class Foo {
+    public static func(): Foo {
+        return new Foo();
+    }
+}
+Foo.func();
+
+try {
+    @decorator()
+    class Foo {
+        public static func(): Foo {
+            return new Foo();
+        }
+    }
+    Foo.func();
+}
+catch (e) {}
+
+
+//// [a.js]
+var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
+    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
+    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+    return c > 3 && r && Object.defineProperty(target, key, r), r;
+};
+function decorator() {
+    return function (target) { };
+}
+var Foo = /** @class */ (function () {
+    function Foo() {
+    }
+    Foo_1 = Foo;
+    Foo.func = function () {
+        return new Foo_1();
+    };
+    var Foo_1;
+    Foo = Foo_1 = __decorate([
+        decorator()
+    ], Foo);
+    return Foo;
+}());
+Foo.func();
+try {
+    var Foo_2 = /** @class */ (function () {
+        function Foo() {
+        }
+        Foo_3 = Foo;
+        Foo.func = function () {
+            return new Foo_3();
+        };
+        var Foo_3;
+        Foo = Foo_3 = __decorate([
+            decorator()
+        ], Foo);
+        return Foo;
+    }());
+    Foo_2.func();
+}
+catch (e) { }
diff --git a/tests/baselines/reference/decoratedBlockScopedClass3.symbols b/tests/baselines/reference/decoratedBlockScopedClass3.symbols
new file mode 100644
index 0000000000000..026ca4a90d387
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass3.symbols
@@ -0,0 +1,51 @@
+=== tests/cases/conformance/decorators/class/a.ts ===
+function decorator() {
+>decorator : Symbol(decorator, Decl(a.ts, 0, 0))
+
+    return (target: new (...args: any[]) => any) => {}
+>target : Symbol(target, Decl(a.ts, 1, 12))
+>args : Symbol(args, Decl(a.ts, 1, 25))
+}
+
+@decorator()
+>decorator : Symbol(decorator, Decl(a.ts, 0, 0))
+
+class Foo {
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+
+    public static func(): Foo {
+>func : Symbol(Foo.func, Decl(a.ts, 5, 11))
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+
+        return new Foo();
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+    }
+}
+Foo.func();
+>Foo.func : Symbol(Foo.func, Decl(a.ts, 5, 11))
+>Foo : Symbol(Foo, Decl(a.ts, 2, 1))
+>func : Symbol(Foo.func, Decl(a.ts, 5, 11))
+
+try {
+    @decorator()
+>decorator : Symbol(decorator, Decl(a.ts, 0, 0))
+
+    class Foo {
+>Foo : Symbol(Foo, Decl(a.ts, 12, 5))
+
+        public static func(): Foo {
+>func : Symbol(Foo.func, Decl(a.ts, 14, 15))
+>Foo : Symbol(Foo, Decl(a.ts, 12, 5))
+
+            return new Foo();
+>Foo : Symbol(Foo, Decl(a.ts, 12, 5))
+        }
+    }
+    Foo.func();
+>Foo.func : Symbol(Foo.func, Decl(a.ts, 14, 15))
+>Foo : Symbol(Foo, Decl(a.ts, 12, 5))
+>func : Symbol(Foo.func, Decl(a.ts, 14, 15))
+}
+catch (e) {}
+>e : Symbol(e, Decl(a.ts, 21, 7))
+
diff --git a/tests/baselines/reference/decoratedBlockScopedClass3.types b/tests/baselines/reference/decoratedBlockScopedClass3.types
new file mode 100644
index 0000000000000..c7315101b9613
--- /dev/null
+++ b/tests/baselines/reference/decoratedBlockScopedClass3.types
@@ -0,0 +1,56 @@
+=== tests/cases/conformance/decorators/class/a.ts ===
+function decorator() {
+>decorator : () => (target: new (...args: any[]) => any) => void
+
+    return (target: new (...args: any[]) => any) => {}
+>(target: new (...args: any[]) => any) => {} : (target: new (...args: any[]) => any) => void
+>target : new (...args: any[]) => any
+>args : any[]
+}
+
+@decorator()
+>decorator() : (target: new (...args: any[]) => any) => void
+>decorator : () => (target: new (...args: any[]) => any) => void
+
+class Foo {
+>Foo : Foo
+
+    public static func(): Foo {
+>func : () => Foo
+
+        return new Foo();
+>new Foo() : Foo
+>Foo : typeof Foo
+    }
+}
+Foo.func();
+>Foo.func() : Foo
+>Foo.func : () => Foo
+>Foo : typeof Foo
+>func : () => Foo
+
+try {
+    @decorator()
+>decorator() : (target: new (...args: any[]) => any) => void
+>decorator : () => (target: new (...args: any[]) => any) => void
+
+    class Foo {
+>Foo : Foo
+
+        public static func(): Foo {
+>func : () => Foo
+
+            return new Foo();
+>new Foo() : Foo
+>Foo : typeof Foo
+        }
+    }
+    Foo.func();
+>Foo.func() : Foo
+>Foo.func : () => Foo
+>Foo : typeof Foo
+>func : () => Foo
+}
+catch (e) {}
+>e : any
+
diff --git a/tests/cases/conformance/decorators/class/decoratedBlockScopedClass1.ts b/tests/cases/conformance/decorators/class/decoratedBlockScopedClass1.ts
new file mode 100644
index 0000000000000..521dd6a31c6aa
--- /dev/null
+++ b/tests/cases/conformance/decorators/class/decoratedBlockScopedClass1.ts
@@ -0,0 +1,16 @@
+// @target: es5
+// @experimentaldecorators: true
+// @emitDecoratorMetadata: true
+// @filename: a.ts
+
+function decorator() {
+    return (target: new (...args: any[]) => any) => {}
+}
+
+@decorator()
+class Foo {
+    public static func(): Foo {
+        return new Foo();
+    }
+}
+Foo.func();
diff --git a/tests/cases/conformance/decorators/class/decoratedBlockScopedClass2.ts b/tests/cases/conformance/decorators/class/decoratedBlockScopedClass2.ts
new file mode 100644
index 0000000000000..7d8de6894f783
--- /dev/null
+++ b/tests/cases/conformance/decorators/class/decoratedBlockScopedClass2.ts
@@ -0,0 +1,19 @@
+// @target: es5
+// @experimentaldecorators: true
+// @emitDecoratorMetadata: true
+// @filename: a.ts
+
+function decorator() {
+    return (target: new (...args: any[]) => any) => {}
+}
+
+try {
+    @decorator()
+    class Foo {
+        public static func(): Foo {
+            return new Foo();
+        }
+    }
+    Foo.func();
+}
+catch (e) {}
diff --git a/tests/cases/conformance/decorators/class/decoratedBlockScopedClass3.ts b/tests/cases/conformance/decorators/class/decoratedBlockScopedClass3.ts
new file mode 100644
index 0000000000000..48eebc559f87a
--- /dev/null
+++ b/tests/cases/conformance/decorators/class/decoratedBlockScopedClass3.ts
@@ -0,0 +1,27 @@
+// @target: es5
+// @experimentaldecorators: true
+// @emitDecoratorMetadata: true
+// @filename: a.ts
+
+function decorator() {
+    return (target: new (...args: any[]) => any) => {}
+}
+
+@decorator()
+class Foo {
+    public static func(): Foo {
+        return new Foo();
+    }
+}
+Foo.func();
+
+try {
+    @decorator()
+    class Foo {
+        public static func(): Foo {
+            return new Foo();
+        }
+    }
+    Foo.func();
+}
+catch (e) {}