diff --git a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
index 3eca30497f..6c32586303 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
@@ -2535,6 +2535,7 @@ InterruptProcess (
         CurrentDebugTimerInitCount = GetApicTimerInitCount ();
         if (mDebugMpContext.DebugTimerInitCount != CurrentDebugTimerInitCount) {
           InitializeDebugTimer (NULL, FALSE);
+          SaveAndSetDebugTimerInterrupt (TRUE);
         }
       }
 
diff --git a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugTimer.c b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugTimer.c
index 25d6468588..4a6ccdb7da 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugTimer.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugTimer.c
@@ -46,6 +46,11 @@ InitializeDebugTimer (
                    );
 
   InitializeApicTimer (ApicTimerDivisor, InitialCount, TRUE, DEBUG_TIMER_VECTOR);
+  //
+  // Disable Debug Timer interrupt to avoid it is delivered before Debug Port
+  // is initialized
+  //
+  DisableApicTimerInterrupt ();
 
   if (DumpFlag) {
     DEBUG ((EFI_D_INFO, "Debug Timer: FSB Clock    = %d\n", PcdGet32(PcdFSBClock)));
diff --git a/SourceLevelDebugPkg/Library/DebugAgent/DxeDebugAgent/DxeDebugAgentLib.c b/SourceLevelDebugPkg/Library/DebugAgent/DxeDebugAgent/DxeDebugAgentLib.c
index aaf342e0ba..56a5e1a170 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/DxeDebugAgent/DxeDebugAgentLib.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/DxeDebugAgent/DxeDebugAgentLib.c
@@ -428,6 +428,10 @@ InitializeDebugAgent (
     //
     InternalConstructorWorker ();
     //
+    // Enable Debug Timer interrupt
+    //
+    SaveAndSetDebugTimerInterrupt (TRUE);
+    //
     // Enable interrupt to receive Debug Timer interrupt
     //
     EnableInterrupts ();
@@ -482,6 +486,10 @@ InitializeDebugAgent (
     //
     SetupDebugAgentEnvironment (Mailbox);
     //
+    // Enable Debug Timer interrupt
+    //
+    SaveAndSetDebugTimerInterrupt (TRUE);
+    //
     // Enable interrupt to receive Debug Timer interrupt
     //
     EnableInterrupts ();
diff --git a/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c b/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c
index 20b6a370d6..e77ff723e3 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.c
@@ -611,6 +611,10 @@ InitializeDebugAgent (
     break;
   }
 
+  //
+  // Enable Debug Timer interrupt
+  //
+  SaveAndSetDebugTimerInterrupt (TRUE);
   //
   // Enable CPU interrupts so debug timer interrupts can be delivered
   //
diff --git a/SourceLevelDebugPkg/Library/DebugAgent/SmmDebugAgent/SmmDebugAgentLib.c b/SourceLevelDebugPkg/Library/DebugAgent/SmmDebugAgent/SmmDebugAgentLib.c
index 4e4e1f536c..6ac5f88dea 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/SmmDebugAgent/SmmDebugAgentLib.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/SmmDebugAgent/SmmDebugAgentLib.c
@@ -284,7 +284,6 @@ InitializeDebugAgent (
     TimerCycle = GetApicTimerInitCount ();
     if (!PeriodicMode || TimerCycle == 0) {
       InitializeDebugTimer (NULL, FALSE);
-      DisableApicTimerInterrupt ();
     }
     Mailbox = GetMailboxPointer ();
     if (GetDebugFlag (DEBUG_AGENT_FLAG_AGENT_IN_PROGRESS) == 1) {
@@ -350,6 +349,10 @@ InitializeDebugAgent (
       //
       InitializeDebugTimer (&DebugTimerFrequency, TRUE);
       UpdateMailboxContent (mMailboxPointer, DEBUG_MAILBOX_DEBUG_TIMER_FREQUENCY, DebugTimerFrequency);
+      //
+      // Enable Debug Timer interrupt and CPU interrupt
+      //
+      SaveAndSetDebugTimerInterrupt (TRUE);
       EnableInterrupts ();
 
       FindAndReportModuleImageInfo (SIZE_4KB);