diff --git a/dom/bluetooth/BluetoothHfpManager.cpp b/dom/bluetooth/BluetoothHfpManager.cpp
index 10198378ecb..fb77c553065 100644
--- a/dom/bluetooth/BluetoothHfpManager.cpp
+++ b/dom/bluetooth/BluetoothHfpManager.cpp
@@ -72,6 +72,12 @@ namespace {
   // Wait for 2 seconds for Dialer processing event 'BLDN'. '2' seconds is a
   // magic number. The mechanism should be revised once we can get call history.
   static int sWaitingForDialingInterval = 2000; //unit: ms
+
+  // Wait 3.7 seconds until Dialer stops playing busy tone. '3' seconds is the
+  // time window set in Dialer and the extra '0.7' second is a magic number.
+  // The mechanism should be revised once we know the exact time at which
+  // Dialer stops playing.
+  static int sBusyToneInterval = 3700; //unit: ms
 } // anonymous namespace
 
 /* CallState for sCINDItems[CINDType::CALL].value
@@ -279,6 +285,17 @@ private:
   int mType;
 };
 
+class BluetoothHfpManager::CloseScoTask : public Task
+{
+private:
+  void Run() MOZ_OVERRIDE
+  {
+    MOZ_ASSERT(gBluetoothHfpManager);
+
+    gBluetoothHfpManager->DisconnectSco();
+  }
+};
+
 static bool
 IsValidDtmf(const char aChar) {
   // Valid DTMF: [*#0-9ABCD]
@@ -1397,8 +1414,17 @@ BluetoothHfpManager::HandleCallStateChanged(uint32_t aCallIndex,
       // -1 is necessary because call 0 is an invalid (padding) call object.
       if (mCurrentCallArray.Length() - 1 ==
           GetNumberOfCalls(nsITelephonyProvider::CALL_STATE_DISCONNECTED)) {
-        // There is no call, close Sco and clear mCurrentCallArray
-        DisconnectSco();
+        // In order to let user hear busy tone via connected Bluetooth headset,
+        // we postpone the timing of dropping SCO.
+        if (prevCallState != nsITelephonyProvider::CALL_STATE_BUSY) {
+          DisconnectSco();
+        } else {
+          // Close Sco later since Dialer is still playing busy tone via HF.
+          MessageLoop::current()->PostDelayedTask(FROM_HERE,
+                                                  new CloseScoTask(),
+                                                  sBusyToneInterval);
+        }
+
         ResetCallArray();
       }
       break;
@@ -1678,11 +1704,17 @@ BluetoothHfpManager::ConnectSco(BluetoothReplyRunnable* aRunnable)
 bool
 BluetoothHfpManager::DisconnectSco()
 {
-  if (!mScoSocket) {
+  if (!IsConnected()) {
     NS_WARNING("BluetoothHfpManager is not connected");
     return false;
   }
 
+  SocketConnectionStatus status = mScoSocket->GetConnectionStatus();
+  if (status != SOCKET_CONNECTED && status != SOCKET_CONNECTING) {
+    NS_WARNING("No SCO exists");
+    return false;
+  }
+
   mScoSocket->Disconnect();
   return true;
 }
@@ -1725,4 +1757,3 @@ BluetoothHfpManager::IsScoConnected()
 }
 
 NS_IMPL_ISUPPORTS1(BluetoothHfpManager, nsIObserver)
-
diff --git a/dom/bluetooth/BluetoothHfpManager.h b/dom/bluetooth/BluetoothHfpManager.h
index 6785e7a84c8..6e2f805854b 100644
--- a/dom/bluetooth/BluetoothHfpManager.h
+++ b/dom/bluetooth/BluetoothHfpManager.h
@@ -93,10 +93,12 @@ public:
   bool IsScoConnected();
 
 private:
+  class CloseScoTask;
   class GetVolumeTask;
   class RespondToBLDNTask;
   class SendRingIndicatorTask;
 
+  friend class CloseScoTask;
   friend class GetVolumeTask;
   friend class RespondToBLDNTask;
   friend class SendRingIndicatorTask;