diff --git a/services/core/java/com/android/server/TelephonyRegistry.java b/services/core/java/com/android/server/TelephonyRegistry.java
index ca74adc2f0c87..e410302457a88 100644
--- a/services/core/java/com/android/server/TelephonyRegistry.java
+++ b/services/core/java/com/android/server/TelephonyRegistry.java
@@ -217,6 +217,8 @@ public class TelephonyRegistry extends ITelephonyRegistry.Stub {
     @TelephonyManager.RadioPowerState
     private int mRadioPowerState = TelephonyManager.RADIO_POWER_UNAVAILABLE;
 
+    private int mPreferredDataSubId = SubscriptionManager.INVALID_SUBSCRIPTION_ID;
+
     private final LocalLog mLocalLog = new LocalLog(100);
 
     private PreciseDataConnectionState mPreciseDataConnectionState =
@@ -756,6 +758,13 @@ public class TelephonyRegistry extends ITelephonyRegistry.Stub {
                             remove(r.binder);
                         }
                     }
+                    if ((events & PhoneStateListener.LISTEN_PREFERRED_DATA_SUBID_CHANGE) != 0) {
+                        try {
+                            r.callback.onPreferredDataSubIdChanged(mPreferredDataSubId);
+                        } catch (RemoteException ex) {
+                            remove(r.binder);
+                        }
+                    }
                     if ((events & PhoneStateListener.LISTEN_RADIO_POWER_STATE_CHANGED) != 0) {
                         try {
                             r.callback.onRadioPowerStateChanged(mRadioPowerState);
@@ -1584,6 +1593,32 @@ public class TelephonyRegistry extends ITelephonyRegistry.Stub {
         }
     }
 
+    public void notifyPreferredDataSubIdChanged(int preferredSubId) {
+        if (!checkNotifyPermission("notifyPreferredDataSubIdChanged()")) {
+            return;
+        }
+
+        if (VDBG) {
+            log("notifyPreferredDataSubIdChanged: preferredSubId=" + preferredSubId);
+        }
+
+        synchronized (mRecords) {
+            mPreferredDataSubId = preferredSubId;
+
+            for (Record r : mRecords) {
+                if (r.matchPhoneStateListenerEvent(
+                        PhoneStateListener.LISTEN_PREFERRED_DATA_SUBID_CHANGE)) {
+                    try {
+                        r.callback.onPreferredDataSubIdChanged(preferredSubId);
+                    } catch (RemoteException ex) {
+                        mRemoveList.add(r.binder);
+                    }
+                }
+            }
+            handleRemoveListLocked();
+        }
+    }
+
     public void notifyRadioPowerStateChanged(@TelephonyManager.RadioPowerState int state) {
         if (!checkNotifyPermission("notifyRadioPowerStateChanged()")) {
             return;
@@ -1647,6 +1682,7 @@ public class TelephonyRegistry extends ITelephonyRegistry.Stub {
             pw.println("mBackgroundCallState=" + mBackgroundCallState);
             pw.println("mVoLteServiceState=" + mVoLteServiceState);
             pw.println("mPhoneCapability=" + mPhoneCapability);
+            pw.println("mPreferredDataSubId=" + mPreferredDataSubId);
             pw.println("mRadioPowerState=" + mRadioPowerState);
 
             pw.decreaseIndent();
diff --git a/telephony/java/android/telephony/PhoneStateListener.java b/telephony/java/android/telephony/PhoneStateListener.java
index 3476db456bb16..0ec85360908be 100644
--- a/telephony/java/android/telephony/PhoneStateListener.java
+++ b/telephony/java/android/telephony/PhoneStateListener.java
@@ -282,6 +282,16 @@ public class PhoneStateListener {
      */
     public static final int LISTEN_PHONE_CAPABILITY_CHANGE                 = 0x00200000;
 
+    /**
+     *  Listen for changes to preferred data subId.
+     *  See {@link SubscriptionManager#setPreferredData(int)}
+     *  for more details.
+     *
+     *  @see #onPreferredDataSubIdChanged
+     *  @hide
+     */
+    public static final int LISTEN_PREFERRED_DATA_SUBID_CHANGE              = 0x00400000;
+
     /**
      *  Listen for changes to the radio power state.
      *
@@ -420,6 +430,9 @@ public class PhoneStateListener {
                     case LISTEN_RADIO_POWER_STATE_CHANGED:
                         PhoneStateListener.this.onRadioPowerStateChanged((int) msg.obj);
                         break;
+                    case LISTEN_PREFERRED_DATA_SUBID_CHANGE:
+                        PhoneStateListener.this.onPreferredDataSubIdChanged((int) msg.obj);
+                        break;
                 }
             }
         };
@@ -670,6 +683,17 @@ public class PhoneStateListener {
         // default implementation empty
     }
 
+    /**
+     * Callback invoked when preferred data subId changes. Requires
+     * the READ_PRIVILEGED_PHONE_STATE permission.
+     * @param subId the new preferred data subId. If it's INVALID_SUBSCRIPTION_ID,
+     *              it means it's unset and defaultDataSub is used to determine which
+     *              modem is preferred.
+     * @hide
+     */
+    public void onPreferredDataSubIdChanged(int subId) {
+        // default implementation empty
+    }
 
     /**
      * Callback invoked when telephony has received notice from a carrier
@@ -806,6 +830,10 @@ public class PhoneStateListener {
         public void onRadioPowerStateChanged(@TelephonyManager.RadioPowerState int state) {
             send(LISTEN_RADIO_POWER_STATE_CHANGED, 0, 0, state);
         }
+
+        public void onPreferredDataSubIdChanged(int subId) {
+            send(LISTEN_PREFERRED_DATA_SUBID_CHANGE, 0, 0, subId);
+        }
     }
 
     /**
diff --git a/telephony/java/android/telephony/SubscriptionManager.java b/telephony/java/android/telephony/SubscriptionManager.java
index a0b020dc16d16..41a6f1b73884f 100644
--- a/telephony/java/android/telephony/SubscriptionManager.java
+++ b/telephony/java/android/telephony/SubscriptionManager.java
@@ -2211,10 +2211,11 @@ public class SubscriptionManager {
      * It's also usually what we set up internet connection on.
      *
      * PreferredData overwrites user setting of default data subscription. And it's used
-     * by ANAS or carrier apps to switch primary and CBRS subscription dynamically in multi-SIM
-     * devices.
+     * by AlternativeNetworkAccessService or carrier apps to switch primary and CBRS
+     * subscription dynamically in multi-SIM devices.
      *
-     * @param slotId which slot is preferred to for cellular data.
+     * @param slotId which slot is preferred to for cellular data. If it's INVALID, it means
+     *               it's unset and defaultDataSubId is used to determine which modem is preferred.
      * @hide
      *
      */
diff --git a/telephony/java/com/android/internal/telephony/IPhoneStateListener.aidl b/telephony/java/com/android/internal/telephony/IPhoneStateListener.aidl
index 86818593a32bf..64ea6083d63d3 100644
--- a/telephony/java/com/android/internal/telephony/IPhoneStateListener.aidl
+++ b/telephony/java/com/android/internal/telephony/IPhoneStateListener.aidl
@@ -53,5 +53,6 @@ oneway interface IPhoneStateListener {
     void onUserMobileDataStateChanged(in boolean enabled);
     void onPhoneCapabilityChanged(in PhoneCapability capability);
     void onRadioPowerStateChanged(in int state);
+    void onPreferredDataSubIdChanged(in int subId);
 }
 
diff --git a/telephony/java/com/android/internal/telephony/ITelephonyRegistry.aidl b/telephony/java/com/android/internal/telephony/ITelephonyRegistry.aidl
index 2f40fcc844f3a..0bbfa9a83b8bf 100644
--- a/telephony/java/com/android/internal/telephony/ITelephonyRegistry.aidl
+++ b/telephony/java/com/android/internal/telephony/ITelephonyRegistry.aidl
@@ -80,4 +80,5 @@ interface ITelephonyRegistry {
     void notifyUserMobileDataStateChangedForPhoneId(in int phoneId, in int subId, in boolean state);
     void notifyPhoneCapabilityChanged(in PhoneCapability capability);
     void notifyRadioPowerStateChanged(in int state);
+    void notifyPreferredDataSubIdChanged(int preferredSubId);
 }