diff --git a/examples/platforms/cc2538/radio.c b/examples/platforms/cc2538/radio.c
index d203f1656..70293b4f5 100644
--- a/examples/platforms/cc2538/radio.c
+++ b/examples/platforms/cc2538/radio.c
@@ -369,6 +369,8 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
         // begin transmit
         HWREG(RFCORE_SFR_RFST) = RFCORE_SFR_RFST_INSTR_TXON;
 
+        otPlatRadioTxStarted(aInstance, aFrame);
+
         while (HWREG(RFCORE_XREG_FSMSTAT1) & RFCORE_XREG_FSMSTAT1_TX_ACTIVE);
 
         otLogDebgPlat(sInstance, "Transmitted %d bytes", aFrame->mLength);
diff --git a/examples/platforms/cc2650/radio.c b/examples/platforms/cc2650/radio.c
index 7ac31b654..cec51aad5 100644
--- a/examples/platforms/cc2650/radio.c
+++ b/examples/platforms/cc2650/radio.c
@@ -1353,6 +1353,8 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
             otEXPECT_ACTION(rfCoreSendTransmitCmd(aFrame->mPsdu, aFrame->mLength - 2) == CMDSTA_Done,
                             error = OT_ERROR_FAILED);
             error = OT_ERROR_NONE;
+
+            otPlatRadioTxStarted(aInstance, aFrame);
         }
     }
 
diff --git a/examples/platforms/da15000/radio.c b/examples/platforms/da15000/radio.c
index cf4acafed..9365fb954 100644
--- a/examples/platforms/da15000/radio.c
+++ b/examples/platforms/da15000/radio.c
@@ -411,6 +411,8 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
     ad_ftdf_send_frame_simple(aFrame->mLength, aFrame->mPsdu, aFrame->mChannel, 0, csmaSuppress); //Prio 0 for all.
     sRadioState = OT_RADIO_STATE_TRANSMIT;
 
+    otPlatRadioTxStarted(aInstance, aFrame);
+
 exit:
     return error;
 }
diff --git a/examples/platforms/efr32/radio.c b/examples/platforms/efr32/radio.c
index 5e82f856c..7a598d6c3 100644
--- a/examples/platforms/efr32/radio.c
+++ b/examples/platforms/efr32/radio.c
@@ -345,6 +345,8 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
     otEXPECT_ACTION(RAIL_TxStartWithOptions(aFrame->mChannel, &txOption, RAIL_CcaCsma, &csmaConfig) == RAIL_STATUS_NO_ERROR,
                     error = OT_ERROR_FAILED);
 
+    otPlatRadioTxStarted(aInstance, aFrame);
+
 exit:
     CORE_EXIT_CRITICAL();
     return error;
diff --git a/examples/platforms/emsk/radio.c b/examples/platforms/emsk/radio.c
index 18b775b26..14681deb2 100644
--- a/examples/platforms/emsk/radio.c
+++ b/examples/platforms/emsk/radio.c
@@ -473,7 +473,6 @@ exit:
 
 void radioTransmitMessage(otInstance *aInstance)
 {
-    (void)aInstance;
     uint8_t header_len = 0;
 
     sTransmitError = OT_ERROR_NONE;
@@ -506,6 +505,8 @@ void radioTransmitMessage(otInstance *aInstance)
 
     mrf24j40_write_short_ctrl_reg(MRF24J40_TXNCON, reg | MRF24J40_TXNTRIG);
 
+    otPlatRadioTxStarted(aInstance, &sTransmitFrame);
+
     int16_t tx_timeout = 500;
     Mrf24StatusTx = 0;
 
diff --git a/examples/platforms/kw41z/radio.c b/examples/platforms/kw41z/radio.c
index 0ca156303..a0bc0ab0c 100644
--- a/examples/platforms/kw41z/radio.c
+++ b/examples/platforms/kw41z/radio.c
@@ -335,8 +335,6 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
     otError status = OT_ERROR_NONE;
     uint32_t timeout;
 
-    (void) aInstance;
-
     otEXPECT_ACTION(((sState != OT_RADIO_STATE_TRANSMIT) &&
                      (sState != OT_RADIO_STATE_DISABLED)), status = OT_ERROR_INVALID_STATE);
 
@@ -379,6 +377,8 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
     /* Unmask SEQ interrupt */
     ZLL->PHY_CTRL &= ~ZLL_PHY_CTRL_SEQMSK_MASK;
 
+    otPlatRadioTxStarted(aInstance, aFrame);
+
 exit:
     return status;
 }
diff --git a/examples/platforms/nrf52840/radio.c b/examples/platforms/nrf52840/radio.c
index e531399b7..f71918291 100644
--- a/examples/platforms/nrf52840/radio.c
+++ b/examples/platforms/nrf52840/radio.c
@@ -92,6 +92,7 @@ static int8_t       sEnergyDetected;
 typedef enum
 {
     kPendingEventSleep,                // Requested to enter Sleep state.
+    kPendingEventTransmit,             // Frame is queued for transmission.
     kPendingEventFrameTransmitted,     // Transmitted frame and received ACK (if requested).
     kPendingEventChannelAccessFailure, // Failed to transmit frame (channel busy).
     kPendingEventEnergyDetectionStart, // Requested to start Energy Detection procedure.
@@ -327,11 +328,12 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
     if (nrf_drv_radio802154_transmit(&aFrame->mPsdu[-1], aFrame->mChannel, aFrame->mPower, true))
     {
         clearPendingEvents();
+        otPlatRadioTxStarted(aInstance, aFrame);
     }
     else
     {
         clearPendingEvents();
-        setPendingEvent(kPendingEventChannelAccessFailure);
+        setPendingEvent(kPendingEventTransmit);
     }
 
     return OT_ERROR_NONE;
@@ -523,6 +525,15 @@ void nrf5RadioProcess(otInstance *aInstance)
         }
     }
 
+    if (isPendingEventSet(kPendingEventTransmit))
+    {
+        if (nrf_drv_radio802154_transmit(sTransmitPsdu, sTransmitFrame.mChannel, sTransmitFrame.mPower, true))
+        {
+            resetPendingEvent(kPendingEventTransmit);
+            otPlatRadioTxStarted(aInstance, &sTransmitFrame);
+        }
+    }
+
     if (isPendingEventSet(kPendingEventFrameTransmitted))
     {
 #if OPENTHREAD_ENABLE_DIAG
@@ -592,6 +603,13 @@ void nrf_drv_radio802154_received(uint8_t *p_data, int8_t power, int8_t lqi)
 {
     otRadioFrame *receivedFrame = NULL;
 
+    if (isPendingEventSet(kPendingEventTransmit))
+    {
+        nrf_drv_radio802154_buffer_free(p_data);
+
+        return;
+    }
+
     for (uint32_t i = 0; i < RADIO_RX_BUFFERS; i++)
     {
         if (sReceivedFrames[i].mPsdu == NULL)
diff --git a/examples/platforms/posix/radio.c b/examples/platforms/posix/radio.c
index e47d17c2a..1b314861b 100644
--- a/examples/platforms/posix/radio.c
+++ b/examples/platforms/posix/radio.c
@@ -508,6 +508,7 @@ void radioSendMessage(otInstance *aInstance)
 {
     sTransmitMessage.mChannel = sTransmitFrame.mChannel;
 
+    otPlatRadioTxStarted(aInstance, &sTransmitFrame);
     radioTransmit(&sTransmitMessage, &sTransmitFrame);
 
     sAckWait = isAckRequested(sTransmitFrame.mPsdu);
diff --git a/include/openthread/platform/radio.h b/include/openthread/platform/radio.h
index b81cd64bc..01eb57f6f 100644
--- a/include/openthread/platform/radio.h
+++ b/include/openthread/platform/radio.h
@@ -388,6 +388,18 @@ otRadioFrame *otPlatRadioGetTransmitBuffer(otInstance *aInstance);
  */
 otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame);
 
+/**
+ * The radio driver calls this method to notify OpenThread that the transmission has started.
+ *
+ * @note  This function should be called by the same thread that executes all of the other OpenThread code. It should
+ *        not be called by ISR or any other task.
+ *
+ * @param[in]  aInstance  A pointer to the OpenThread instance structure.
+ * @param[in]  aFrame     A pointer to the frame that is being transmitted.
+ *
+ */
+extern void otPlatRadioTxStarted(otInstance *aInstance, otRadioFrame *aFrame);
+
 /**
  * The radio driver calls this method to notify OpenThread that the transmission has completed,
  * this callback pass up the ACK frame, new add platforms should use this callback function.
diff --git a/src/core/mac/mac.cpp b/src/core/mac/mac.cpp
index 131fbf807..384cc2acc 100644
--- a/src/core/mac/mac.cpp
+++ b/src/core/mac/mac.cpp
@@ -832,12 +832,6 @@ void Mac::HandleBeginTransmit(void)
 
     assert(error == OT_ERROR_NONE);
 
-    if (sendFrame.GetAckRequest() && !(otPlatRadioGetCaps(GetInstance()) & OT_RADIO_CAPS_ACK_TIMEOUT))
-    {
-        mMacTimer.Start(kAckTimeout);
-        otLogDebgMac(GetInstance(), "Ack timer start");
-    }
-
     if (mPcapCallback)
     {
         sendFrame.mDidTX = true;
@@ -856,6 +850,26 @@ exit:
     }
 }
 
+extern "C" void otPlatRadioTxStarted(otInstance *aInstance, otRadioFrame *aFrame)
+{
+    otLogFuncEntry();
+
+    aInstance->mThreadNetif.GetMac().TransmitStartedTask(aFrame);
+
+    otLogFuncExit();
+}
+
+void Mac::TransmitStartedTask(otRadioFrame *aFrame)
+{
+    Frame *frame = static_cast<Frame *>(aFrame);
+
+    if (frame->GetAckRequest() && !(otPlatRadioGetCaps(GetInstance()) & OT_RADIO_CAPS_ACK_TIMEOUT))
+    {
+        mMacTimer.Start(kAckTimeout);
+        otLogDebgMac(GetInstance(), "Ack timer start");
+    }
+}
+
 #if OPENTHREAD_CONFIG_LEGACY_TRANSMIT_DONE
 extern "C" void otPlatRadioTransmitDone(otInstance *aInstance, otRadioFrame *aFrame, bool aRxPending,
                                         otError aError)
diff --git a/src/core/mac/mac.hpp b/src/core/mac/mac.hpp
index 90a233413..21caf3d8f 100644
--- a/src/core/mac/mac.hpp
+++ b/src/core/mac/mac.hpp
@@ -501,6 +501,13 @@ public:
      */
     void ReceiveDoneTask(Frame *aFrame, otError aError);
 
+    /**
+     * This method is called to handle transmission start events.
+     *
+     * @param[in]  aFrame  A pointer to the frame that is transmitted.
+     */
+    void TransmitStartedTask(otRadioFrame *aFrame);
+
 #if OPENTHREAD_CONFIG_LEGACY_TRANSMIT_DONE
     /**
      * This method is called to handle transmit events.
diff --git a/tests/unit/test_diag.cpp b/tests/unit/test_diag.cpp
index e881bc946..45cb14576 100644
--- a/tests/unit/test_diag.cpp
+++ b/tests/unit/test_diag.cpp
@@ -70,6 +70,11 @@ extern "C" void otPlatRadioReceiveDone(otInstance *, otRadioFrame *aFrame, otErr
     (void)aError;
 }
 
+extern "C" void otPlatRadioTxStarted(otInstance *, otRadioFrame *aFrame)
+{
+    (void) aFrame;
+}
+
 
 /**
  *  diagnostics module tests