diff --git a/Makefile b/Makefile
index a7ee97ecabeae8..27ce567d234742 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,7 @@ TS_FILES = \
 	msg.pb.js \
 	os.ts \
 	runtime.ts \
+	timers.ts \
 	util.ts
 
 deno: assets.go msg.pb.go main.go
diff --git a/main.go b/main.go
index be7ad541f21b78..39ba9cb87ed6f1 100644
--- a/main.go
+++ b/main.go
@@ -9,8 +9,13 @@ import (
 	"os"
 	"path"
 	"runtime"
+	"sync"
+	"time"
 )
 
+var wg sync.WaitGroup
+var resChan chan *Msg
+
 func SourceCodeHash(filename string, sourceCodeBuf []byte) string {
 	h := md5.New()
 	h.Write([]byte(filename))
@@ -70,6 +75,22 @@ func HandleSourceCodeCache(filename string, sourceCode string,
 	return out
 }
 
+func HandleTimerStart(id int32, interval bool, duration int32) []byte {
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		time.Sleep(time.Duration(duration) * time.Millisecond)
+		resChan <- &Msg{
+			Payload: &Msg_TimerReady{
+				TimerReady: &TimerReadyMsg{
+					Id: id,
+				},
+			},
+		}
+	}()
+	return nil
+}
+
 func UserHomeDir() string {
 	if runtime.GOOS == "windows" {
 		home := os.Getenv("HOMEDRIVE") + os.Getenv("HOMEPATH")
@@ -121,7 +142,11 @@ func recv(buf []byte) []byte {
 		return HandleSourceCodeFetch(payload.Filename)
 	case *Msg_SourceCodeCache:
 		payload := msg.GetSourceCodeCache()
-		return HandleSourceCodeCache(payload.Filename, payload.SourceCode, payload.OutputCode)
+		return HandleSourceCodeCache(payload.Filename, payload.SourceCode,
+			payload.OutputCode)
+	case *Msg_TimerStart:
+		payload := msg.GetTimerStart()
+		return HandleTimerStart(payload.Id, payload.Interval, payload.Duration)
 	default:
 		panic("Unexpected message")
 	}
@@ -137,6 +162,9 @@ func main() {
 	cwd, err := os.Getwd()
 	check(err)
 
+	resChan = make(chan *Msg)
+	doneChan := make(chan bool)
+
 	out, err := proto.Marshal(&Msg{
 		Payload: &Msg_Start{
 			Start: &StartMsg{
@@ -151,4 +179,23 @@ func main() {
 		os.Stderr.WriteString(err.Error())
 		os.Exit(1)
 	}
+
+	// In a goroutine, we wait on for all goroutines to complete (for example
+	// timers). We use this to signal to the main thread to exit.
+	go func() {
+		wg.Wait()
+		doneChan <- true
+	}()
+
+	for {
+		select {
+		case msg := <-resChan:
+			out, err := proto.Marshal(msg)
+			err = worker.SendBytes(out)
+			check(err)
+		case <-doneChan:
+			// All goroutines have completed. Now we can exit main().
+			return
+		}
+	}
 }
diff --git a/main.ts b/main.ts
index e840e5b5a91999..d853cc2b12e08d 100644
--- a/main.ts
+++ b/main.ts
@@ -1,6 +1,7 @@
 import { main as pb } from "./msg.pb";
 import "./util";
 import * as runtime from "./runtime";
+import * as timers from "./timers";
 import * as path from "path";
 
 function start(cwd: string, argv: string[]): void {
@@ -17,6 +18,9 @@ V8Worker2.recv((ab: ArrayBuffer) => {
     case "start":
       start(msg.start.cwd, msg.start.argv);
       break;
+    case "timerReady":
+      timers.timerReady(msg.timerReady.id, msg.timerReady.done);
+      break;
     default:
       console.log("Unknown message", msg);
       break;
diff --git a/msg.proto b/msg.proto
index 181dcc551e9d7a..1ab78b6906f0df 100644
--- a/msg.proto
+++ b/msg.proto
@@ -10,6 +10,8 @@ message Msg {
     SourceCodeFetchResMsg source_code_fetch_res = 12;
     SourceCodeCacheMsg source_code_cache = 13;
     ExitMsg exit = 14;
+    TimerStartMsg timer_start = 15;
+    TimerReadyMsg timer_ready = 16;
   }
 }
 
@@ -33,3 +35,14 @@ message SourceCodeCacheMsg {
 }
 
 message ExitMsg { int32 code = 1; }
+
+message TimerStartMsg {
+  int32 id = 1;
+  bool interval = 2;
+  int32 duration = 3; // In milliseconds.
+}
+
+message TimerReadyMsg {
+  int32 id = 1;
+  bool done = 2;
+}
diff --git a/os.ts b/os.ts
index d09026c6ccd9ed..44c3ab50882411 100644
--- a/os.ts
+++ b/os.ts
@@ -35,7 +35,7 @@ function typedArrayToArrayBuffer(ta: TypedArray): ArrayBuffer {
   return ab as ArrayBuffer;
 }
 
-function sendMsgFromObject(obj: pb.IMsg): null | pb.Msg {
+export function sendMsgFromObject(obj: pb.IMsg): null | pb.Msg {
   const msg = pb.Msg.fromObject(obj);
   const ui8 = pb.Msg.encode(msg).finish();
   const ab = typedArrayToArrayBuffer(ui8);
diff --git a/testdata/004_set_timeout.ts b/testdata/004_set_timeout.ts
new file mode 100644
index 00000000000000..fe55e31ba02f9f
--- /dev/null
+++ b/testdata/004_set_timeout.ts
@@ -0,0 +1,5 @@
+setTimeout(function() {
+  console.log("World");
+}, 10);
+
+console.log("Hello");
diff --git a/testdata/004_set_timeout.ts.out b/testdata/004_set_timeout.ts.out
new file mode 100644
index 00000000000000..f9264f7fbd31ae
--- /dev/null
+++ b/testdata/004_set_timeout.ts.out
@@ -0,0 +1,2 @@
+Hello
+World
diff --git a/timers.ts b/timers.ts
new file mode 100644
index 00000000000000..ed84c00e9df9d7
--- /dev/null
+++ b/timers.ts
@@ -0,0 +1,43 @@
+import { _global } from "./util";
+import { sendMsgFromObject } from "./os";
+
+let nextTimerId = 1;
+
+// tslint:disable-next-line:no-any
+type TimerCallback = (...args: any[]) => void;
+
+interface Timer {
+  id: number;
+  cb: TimerCallback;
+  interval: boolean;
+  duration: number; // milliseconds
+}
+
+const timers = new Map<number, Timer>();
+
+export function setTimeout(cb: TimerCallback, duration: number): number {
+  const timer = {
+    id: nextTimerId++,
+    interval: false,
+    duration,
+    cb
+  };
+  timers.set(timer.id, timer);
+  sendMsgFromObject({
+    timerStart: {
+      id: timer.id,
+      interval: false,
+      duration
+    }
+  });
+  return timer.id;
+}
+_global["setTimeout"] = setTimeout;
+
+export function timerReady(id: number, done: boolean): void {
+  const timer = timers.get(id);
+  timer.cb();
+  if (done) {
+    timers.delete(id);
+  }
+}