diff --git a/src/printer.js b/src/printer.js
index bf8234f1..52f493c8 100644
--- a/src/printer.js
+++ b/src/printer.js
@@ -332,7 +332,11 @@ function genericPrintNoParens(path, options, print, args) {
       ]);
     case "FunctionDeclaration":
     case "FunctionExpression":
-      return printFunctionDeclaration(path, print, options);
+      if (isNodeStartingWithDeclare(n, options)) {
+        parts.push("declare ");
+      }
+      parts.push(printFunctionDeclaration(path, print, options));
+      return concat(parts);
     case "ArrowFunctionExpression": {
       if (n.async) parts.push("async ");
 
@@ -996,6 +1000,7 @@ function genericPrintNoParens(path, options, print, args) {
       }, "declarations");
 
       parts = [
+        isNodeStartingWithDeclare(n, options) ? "declare " : "",
         n.kind,
         " ",
         printed[0],
@@ -1476,7 +1481,11 @@ function genericPrintNoParens(path, options, print, args) {
     case "ClassDeclaration":
     case "ClassExpression":
     case "TSAbstractClassDeclaration":
-      return concat(printClass(path, options, print));
+      if (isNodeStartingWithDeclare(n, options)) {
+        parts.push("declare ");
+      }
+      parts.push(concat(printClass(path, options, print)));
+      return concat(parts);
     case "TemplateElement":
       return join(literalline, n.value.raw.split("\n"));
     case "TemplateLiteral":
@@ -1684,7 +1693,7 @@ function genericPrintNoParens(path, options, print, args) {
     case "InterfaceDeclaration": {
       if (
         n.type === "DeclareInterface" ||
-        isFlowNodeStartingWithDeclare(n, options)
+        isNodeStartingWithDeclare(n, options)
       ) {
         parts.push("declare ");
       }
@@ -1823,7 +1832,7 @@ function genericPrintNoParens(path, options, print, args) {
     case "TypeAlias": {
       if (
         n.type === "DeclareTypeAlias" ||
-        isFlowNodeStartingWithDeclare(n, options)
+        isNodeStartingWithDeclare(n, options)
       ) {
         parts.push("declare ");
       }
@@ -1933,7 +1942,7 @@ function genericPrintNoParens(path, options, print, args) {
       return concat([path.call(print, "elementType"), "[]"]);
     case "TSPropertySignature":
       parts.push(path.call(print, "name"));
-      parts.push(": ")
+      parts.push(": ");
       parts.push(path.call(print, "typeAnnotation"));
 
       return concat(parts);
@@ -2133,7 +2142,6 @@ function printStatementSequence(path, options, print) {
       parts.push(stmtPrinted);
     }
 
-
     if (!options.semi && isClass) {
       if (classPropMayCauseASIProblems(stmtPath)) {
         parts.push(";");
@@ -2562,7 +2570,7 @@ function printReturnType(path, print) {
 
   // prepend colon to TypeScript type annotation
   if (n.returnType && n.returnType.typeAnnotation) {
-    parts.unshift(": ")
+    parts.unshift(": ");
   }
 
   if (n.predicate) {
@@ -3658,14 +3666,16 @@ function isTypeAnnotationAFunction(node) {
   );
 }
 
-function isFlowNodeStartingWithDeclare(node, options) {
-  if (options.parser !== "flow") {
+function isNodeStartingWithDeclare(node, options) {
+  if (!(options.parser === "flow" || options.parser === "typescript")) {
     return false;
   }
-
-  return options.originalText
-    .slice(0, util.locStart(node))
-    .match(/declare\s*$/);
+  return (
+    options.originalText.slice(0, util.locStart(node)).match(/declare\s*$/) ||
+    options.originalText
+      .slice(node.range[0], node.range[1])
+      .startsWith("declare ")
+  );
 }
 
 function printArrayItems(path, options, printPath, print) {
diff --git a/tests/typescript/conformance/ambient/__snapshots__/jsfmt.spec.js.snap b/tests/typescript/conformance/ambient/__snapshots__/jsfmt.spec.js.snap
new file mode 100644
index 00000000..ad119aa1
--- /dev/null
+++ b/tests/typescript/conformance/ambient/__snapshots__/jsfmt.spec.js.snap
@@ -0,0 +1,58 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`ambientDeclarations.ts 1`] = `
+declare var n;
+
+declare var m: string;
+
+declare function fn1();
+
+declare function fn2(n: string): number;
+
+declare function fn3(n: string): number;
+declare function fn4(n: number, y: number): string;
+
+declare function fn5(x, y?);
+declare function fn6(e?);
+declare function fn7(x, y?, ...z);
+declare function fn8(y?, ...z: number[]);
+declare function fn9(...q: {}[]);
+declare function fn10<T>(...q: T[]);
+
+declare class cls {
+    constructor();
+    method(): cls;
+    static static(p): number;
+    static q;
+    private fn();
+    private static fns();
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+declare var n;
+
+declare var m: string;
+
+declare function fn1()
+
+declare function fn2(n: string): number
+
+declare function fn3(n: string): number
+declare function fn4(n: number, y: number): string
+
+declare function fn5(x, y?)
+declare function fn6(e?)
+declare function fn7(x, y?, ...z)
+declare function fn8(y?, ...z: number[])
+declare function fn9(...q: {}[])
+declare function fn10<T>(...q: T[])
+
+declare class cls {
+  constructor();
+  method(): cls;
+  static static(p): number;
+  static q;
+  private fn();
+  static private fns();
+}
+
+`;
diff --git a/tests/typescript/conformance/ambient/ambientDeclarations.ts b/tests/typescript/conformance/ambient/ambientDeclarations.ts
new file mode 100644
index 00000000..9cc2cf20
--- /dev/null
+++ b/tests/typescript/conformance/ambient/ambientDeclarations.ts
@@ -0,0 +1,26 @@
+declare var n;
+
+declare var m: string;
+
+declare function fn1();
+
+declare function fn2(n: string): number;
+
+declare function fn3(n: string): number;
+declare function fn4(n: number, y: number): string;
+
+declare function fn5(x, y?);
+declare function fn6(e?);
+declare function fn7(x, y?, ...z);
+declare function fn8(y?, ...z: number[]);
+declare function fn9(...q: {}[]);
+declare function fn10<T>(...q: T[]);
+
+declare class cls {
+    constructor();
+    method(): cls;
+    static static(p): number;
+    static q;
+    private fn();
+    private static fns();
+}
diff --git a/tests/typescript/conformance/ambient/jsfmt.spec.js b/tests/typescript/conformance/ambient/jsfmt.spec.js
new file mode 100644
index 00000000..bc085c48
--- /dev/null
+++ b/tests/typescript/conformance/ambient/jsfmt.spec.js
@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "typescript" });
diff --git a/tests/typescript/conformance/types/thisType/__snapshots__/jsfmt.spec.js.snap b/tests/typescript/conformance/types/thisType/__snapshots__/jsfmt.spec.js.snap
index 9d1319ff..4a037b5d 100644
--- a/tests/typescript/conformance/types/thisType/__snapshots__/jsfmt.spec.js.snap
+++ b/tests/typescript/conformance/types/thisType/__snapshots__/jsfmt.spec.js.snap
@@ -5,7 +5,7 @@ declare class MyArray<T> extends Array<T> {
     sort(compareFn?: (a: T, b: T) => number): this;
 }
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-class MyArray<T> extends Array {
+declare class MyArray<T> extends Array {
   sort(compareFn?: (a: T, b: T) => number): this;
 }
 
diff --git a/tests/typescript/custom/declare/__snapshots__/jsfmt.spec.js.snap b/tests/typescript/custom/declare/__snapshots__/jsfmt.spec.js.snap
new file mode 100644
index 00000000..5a14f2b5
--- /dev/null
+++ b/tests/typescript/custom/declare/__snapshots__/jsfmt.spec.js.snap
@@ -0,0 +1,25 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`declareModifier.d.ts 1`] = `
+
+declare function a();
+
+declare const b: string;
+
+declare var c: number;
+
+declare let d: any;
+
+declare class e {}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+declare function a()
+
+declare const b: string;
+
+declare var c: number;
+
+declare let d: any;
+
+declare class e {}
+
+`;
diff --git a/tests/typescript/custom/declare/declareModifier.d.ts b/tests/typescript/custom/declare/declareModifier.d.ts
new file mode 100644
index 00000000..6c2d3628
--- /dev/null
+++ b/tests/typescript/custom/declare/declareModifier.d.ts
@@ -0,0 +1,10 @@
+
+declare function a();
+
+declare const b: string;
+
+declare var c: number;
+
+declare let d: any;
+
+declare class e {}
diff --git a/tests/typescript/custom/declare/jsfmt.spec.js b/tests/typescript/custom/declare/jsfmt.spec.js
new file mode 100644
index 00000000..bc085c48
--- /dev/null
+++ b/tests/typescript/custom/declare/jsfmt.spec.js
@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "typescript" });