diff --git a/services/core/java/com/android/server/BinaryTransparencyService.java b/services/core/java/com/android/server/BinaryTransparencyService.java
index 68722d207ae3c..d485441a605fe 100644
--- a/services/core/java/com/android/server/BinaryTransparencyService.java
+++ b/services/core/java/com/android/server/BinaryTransparencyService.java
@@ -29,8 +29,11 @@ import android.app.job.JobService;
 import android.compat.annotation.ChangeId;
 import android.content.ComponentName;
 import android.content.Context;
+import android.content.pm.ApexStagedEvent;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.IBackgroundInstallControlService;
+import android.content.pm.IPackageManagerNative;
+import android.content.pm.IStagedApexObserver;
 import android.content.pm.InstallSourceInfo;
 import android.content.pm.ModuleInfo;
 import android.content.pm.PackageInfo;
@@ -129,7 +132,6 @@ public class BinaryTransparencyService extends SystemService {
     private String mVbmetaDigest;
     // the system time (in ms) the last measurement was taken
     private long mMeasurementsLastRecordedMs;
-    private PackageManagerInternal mPackageManagerInternal;
 
     /**
      * Guards whether or not measurements of MBA to be performed. When this change is enabled,
@@ -1047,7 +1049,6 @@ public class BinaryTransparencyService extends SystemService {
         mServiceImpl = new BinaryTransparencyServiceImpl();
         mVbmetaDigest = VBMETA_DIGEST_UNINITIALIZED;
         mMeasurementsLastRecordedMs = 0;
-        mPackageManagerInternal = LocalServices.getService(PackageManagerInternal.class);
     }
 
     /**
@@ -1062,38 +1063,6 @@ public class BinaryTransparencyService extends SystemService {
         } catch (Throwable t) {
             Slog.e(TAG, "Failed to start BinaryTransparencyService.", t);
         }
-
-        // register a package observer to detect updates to preloads
-        mPackageManagerInternal.getPackageList(new PackageManagerInternal.PackageListObserver() {
-            @Override
-            public void onPackageAdded(String packageName, int uid) {
-
-            }
-
-            @Override
-            public void onPackageChanged(String packageName, int uid) {
-                // check if the updated package is a preloaded app.
-                PackageManager pm = mContext.getPackageManager();
-                try {
-                    pm.getPackageInfo(packageName, PackageManager.PackageInfoFlags.of(
-                            PackageManager.MATCH_FACTORY_ONLY));
-                } catch (PackageManager.NameNotFoundException e) {
-                    // this means that this package is not a preloaded app
-                    return;
-                }
-
-                Slog.d(TAG, "Preload " + packageName + " was updated. Scheduling measurement...");
-                UpdateMeasurementsJobService.scheduleBinaryMeasurements(mContext,
-                        BinaryTransparencyService.this);
-            }
-
-            @Override
-            public void onPackageRemoved(String packageName, int uid) {
-
-            }
-        });
-
-        // TODO(b/264428429): Register observer for updates to APEXs.
     }
 
     /**
@@ -1104,19 +1073,22 @@ public class BinaryTransparencyService extends SystemService {
      */
     @Override
     public void onBootPhase(int phase) {
-
-        // we are only interested in doing things at PHASE_BOOT_COMPLETED
-        if (phase == PHASE_BOOT_COMPLETED) {
-            Slog.i(TAG, "Boot completed. Getting VBMeta Digest.");
-            getVBMetaDigestInformation();
-
-            // to avoid the risk of holding up boot time, computations to measure APEX, Module, and
-            // MBA digests are scheduled here, but only executed when the device is idle and plugged
-            // in.
-            Slog.i(TAG, "Scheduling measurements to be taken.");
-            UpdateMeasurementsJobService.scheduleBinaryMeasurements(mContext,
-                    BinaryTransparencyService.this);
+        // so far we are only doing things in the PHASE_BOOT_COMPLETED phase
+        if (phase != PHASE_BOOT_COMPLETED) {
+            return;
         }
+
+        Slog.i(TAG, "Boot completed. Getting VBMeta Digest.");
+        getVBMetaDigestInformation();
+
+        // to avoid the risk of holding up boot time, computations to measure APEX, Module, and
+        // MBA digests are scheduled here, but only executed when the device is idle and plugged
+        // in.
+        Slog.i(TAG, "Scheduling measurements to be taken.");
+        UpdateMeasurementsJobService.scheduleBinaryMeasurements(mContext,
+                BinaryTransparencyService.this);
+
+        registerPackageUpdateObservers();
     }
 
     /**
@@ -1212,6 +1184,67 @@ public class BinaryTransparencyService extends SystemService {
         FrameworkStatsLog.write(FrameworkStatsLog.VBMETA_DIGEST_REPORTED, mVbmetaDigest);
     }
 
+    /**
+     * Register observers for APK and APEX updates.
+     * The observers will be invoked when i) APK update and ii) APEX staging happens. This will
+     * then be used as signals to schedule measurement for the relevant binaries.
+     */
+    private void registerPackageUpdateObservers() {
+        Slog.d(TAG, "Registering APK updates...");
+        // first, register a package observer to detect updates to preloads
+        PackageManagerInternal pmi = LocalServices.getService(PackageManagerInternal.class);
+        pmi.getPackageList(new PackageManagerInternal.PackageListObserver() {
+            @Override
+            public void onPackageAdded(String packageName, int uid) {
+            }
+
+            @Override
+            public void onPackageChanged(String packageName, int uid) {
+                // check if the updated package is a preloaded app.
+                PackageManager pm = mContext.getPackageManager();
+                try {
+                    pm.getPackageInfo(packageName, PackageManager.PackageInfoFlags.of(
+                            PackageManager.MATCH_FACTORY_ONLY));
+                } catch (PackageManager.NameNotFoundException e) {
+                    // this means that this package is not a preloaded app
+                    return;
+                }
+
+                Slog.d(TAG, "Preload " + packageName + " was updated. Scheduling measurement...");
+                UpdateMeasurementsJobService.scheduleBinaryMeasurements(mContext,
+                        BinaryTransparencyService.this);
+            }
+
+            @Override
+            public void onPackageRemoved(String packageName, int uid) {
+            }
+        });
+
+        // then, register an observer for staged APEXs
+        Slog.d(TAG, "Registering APEX updates...");
+        IPackageManagerNative iPackageManagerNative = IPackageManagerNative.Stub.asInterface(
+                ServiceManager.getService("package_native"));
+        if (iPackageManagerNative == null) {
+            Slog.e(TAG, "IPackageManagerNative is null");
+            return;
+        }
+
+        try {
+            iPackageManagerNative.registerStagedApexObserver(new IStagedApexObserver.Stub() {
+                @Override
+                public void onApexStaged(ApexStagedEvent event) throws RemoteException {
+                    Slog.d(TAG, "A new APEX has been staged for update. There are currently "
+                            + event.stagedApexModuleNames.length + " APEX(s) staged for update. "
+                            + "Scheduling measurement...");
+                    UpdateMeasurementsJobService.scheduleBinaryMeasurements(mContext,
+                            BinaryTransparencyService.this);
+                }
+            });
+        } catch (RemoteException e) {
+            Slog.e(TAG, "Failed to register a StagedApexObserver.");
+        }
+    }
+
     private String translateContentDigestAlgorithmIdToString(int algorithmId) {
         switch (algorithmId) {
             case ApkSigningBlockUtils.CONTENT_DIGEST_CHUNKED_SHA256: