diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 07ec5023d5b..1ce5b51c66d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -5889,16 +5889,20 @@ namespace ts {
 
                 const sourceSignatures = getSignaturesOfType(source, kind);
                 const targetSignatures = getSignaturesOfType(target, kind);
-                if (kind === SignatureKind.Construct && sourceSignatures.length && targetSignatures.length &&
-                    isAbstractConstructorType(source) && !isAbstractConstructorType(target)) {
-                    // An abstract constructor type is not assignable to a non-abstract constructor type
-                    // as it would otherwise be possible to new an abstract class. Note that the assignablity
-                    // check we perform for an extends clause excludes construct signatures from the target,
-                    // so this check never proceeds.
-                    if (reportErrors) {
-                        reportError(Diagnostics.Cannot_assign_an_abstract_constructor_type_to_a_non_abstract_constructor_type);
+                if (kind === SignatureKind.Construct && sourceSignatures.length && targetSignatures.length) {
+                    if (isAbstractConstructorType(source) && !isAbstractConstructorType(target)) {
+                        // An abstract constructor type is not assignable to a non-abstract constructor type
+                        // as it would otherwise be possible to new an abstract class. Note that the assignablity
+                        // check we perform for an extends clause excludes construct signatures from the target,
+                        // so this check never proceeds.
+                        if (reportErrors) {
+                            reportError(Diagnostics.Cannot_assign_an_abstract_constructor_type_to_a_non_abstract_constructor_type);
+                        }
+                        return Ternary.False;
+                    }
+                    if (!constructorRelatedTo(sourceSignatures[0], targetSignatures[0], reportErrors)) {
+                        return Ternary.False;
                     }
-                    return Ternary.False;
                 }
 
                 let result = Ternary.True;
@@ -6052,6 +6056,32 @@ namespace ts {
                 }
                 return Ternary.True;
             }
+
+            function constructorRelatedTo(sourceSignature: Signature, targetSignature: Signature, reportErrors: boolean) {
+                if (sourceSignature && targetSignature && sourceSignature.declaration && targetSignature.declaration) {
+                    const sourceAccessibility = sourceSignature.declaration.flags & (NodeFlags.Private | NodeFlags.Protected);
+                    const targetAccessibility = targetSignature.declaration.flags & (NodeFlags.Private | NodeFlags.Protected);
+
+                    const isRelated = sourceAccessibility === targetAccessibility;
+                    if (!isRelated && reportErrors) {
+                        reportError(Diagnostics.Cannot_assign_a_0_constructor_type_to_a_1_constructor_type, flagsToString(sourceAccessibility), flagsToString(targetAccessibility));
+                    }
+
+                    return isRelated;
+                }
+
+                return true;
+
+                function flagsToString(flags: NodeFlags) {
+                    if (flags === NodeFlags.Private) {
+                        return "private";
+                    }
+                    if (flags === NodeFlags.Protected) {
+                        return "protected";
+                    }
+                    return "public";
+                }
+            }
         }
 
         // Return true if the given type is the constructor type for an abstract class
@@ -10103,6 +10133,9 @@ namespace ts {
             // that the user will not add any.
             const constructSignatures = getSignaturesOfType(expressionType, SignatureKind.Construct);
             if (constructSignatures.length) {
+                if (!isConstructorAccessible(node, constructSignatures[0])) {
+                    return resolveErrorCall(node);
+                }
                 return resolveCall(node, constructSignatures, candidatesOutArray);
             }
 
@@ -10123,6 +10156,37 @@ namespace ts {
             return resolveErrorCall(node);
         }
 
+        function isConstructorAccessible(node: NewExpression, signature: Signature) {
+            if (!signature || !signature.declaration) {
+                return true;
+            }
+
+            const declaration = signature.declaration;
+            const flags = declaration.flags;
+
+            // Public constructor is accessible.
+            if (!(flags & (NodeFlags.Private | NodeFlags.Protected))) {
+                return true;
+            }
+
+            const declaringClass = <InterfaceType>getDeclaredTypeOfSymbol(declaration.parent.symbol);
+            const enclosingClassDeclaration = getContainingClass(node);
+            const enclosingClass = enclosingClassDeclaration ? <InterfaceType>getDeclaredTypeOfSymbol(getSymbolOfNode(enclosingClassDeclaration)) : undefined;
+
+            // A private or protected constructor can only be instantiated within it's own class 
+            if (declaringClass !== enclosingClass) {
+                if (flags & NodeFlags.Private) {
+                    error(node, Diagnostics.Constructor_of_type_0_is_private_and_only_accessible_within_class_1, signatureToString(signature), typeToString(declaringClass));
+                }
+                if (flags & NodeFlags.Protected) {
+                    error(node, Diagnostics.Constructor_of_type_0_is_protected_and_only_accessible_within_class_1, signatureToString(signature), typeToString(declaringClass));
+                }
+                return false;
+            }
+
+            return true;
+        }
+
         function resolveTaggedTemplateExpression(node: TaggedTemplateExpression, candidatesOutArray: Signature[]): Signature {
             const tagType = checkExpression(node.tag);
             const apparentType = getApparentType(tagType);
@@ -12059,7 +12123,7 @@ namespace ts {
                             error(o.name, Diagnostics.Overload_signatures_must_all_be_ambient_or_non_ambient);
                         }
                         else if (deviation & (NodeFlags.Private | NodeFlags.Protected)) {
-                            error(o.name, Diagnostics.Overload_signatures_must_all_be_public_private_or_protected);
+                            error(o.name || o, Diagnostics.Overload_signatures_must_all_be_public_private_or_protected);
                         }
                         else if (deviation & NodeFlags.Abstract) {
                             error(o.name, Diagnostics.Overload_signatures_must_all_be_abstract_or_not_abstract);
@@ -13928,6 +13992,7 @@ namespace ts {
                 if (baseTypes.length && produceDiagnostics) {
                     const baseType = baseTypes[0];
                     const staticBaseType = getBaseConstructorTypeOfClass(type);
+                    checkBaseTypeAccessibility(staticBaseType, baseTypeNode);
                     checkSourceElement(baseTypeNode.expression);
                     if (baseTypeNode.typeArguments) {
                         forEach(baseTypeNode.typeArguments, checkSourceElement);
@@ -13983,6 +14048,16 @@ namespace ts {
             }
         }
 
+        function checkBaseTypeAccessibility(type: ObjectType, node: ExpressionWithTypeArguments) {
+            const signatures = getSignaturesOfType(type, SignatureKind.Construct);
+            if (signatures.length) {
+                const declaration = signatures[0].declaration;
+                if (declaration && declaration.flags & NodeFlags.Private) {
+                    error(node, Diagnostics.Cannot_extend_private_class_0, (<Identifier>node.expression).text);
+                }
+            }
+        }
+
         function getTargetSymbol(s: Symbol) {
             // if symbol is instantiated its flags are not copied from the 'target'
             // so we'll need to get back original 'target' symbol to work with correct set of flags
@@ -16348,12 +16423,6 @@ namespace ts {
                 if (flags & NodeFlags.Abstract) {
                     return grammarErrorOnNode(lastStatic, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "abstract");
                 }
-                else if (flags & NodeFlags.Protected) {
-                    return grammarErrorOnNode(lastProtected, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "protected");
-                }
-                else if (flags & NodeFlags.Private) {
-                    return grammarErrorOnNode(lastPrivate, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "private");
-                }
                 else if (flags & NodeFlags.Async) {
                     return grammarErrorOnNode(lastAsync, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "async");
                 }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index c848ebc3a10..2ee388ff42e 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1823,6 +1823,22 @@
         "category": "Error",
         "code": 2671
     },
+    "Cannot assign a '{0}' constructor type to a '{1}' constructor type.": {
+        "category": "Error",
+        "code": 2672
+    },
+    "Constructor of type '{0}' is private and only accessible within class '{1}'.": {
+        "category": "Error",
+        "code": 2673
+    },
+    "Constructor of type '{0}' is protected and only accessible within class '{1}'.": {
+        "category": "Error",
+        "code": 2674
+    },
+    "Cannot extend private class '{0}'.": {
+        "category": "Error",
+        "code": 2675
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000