diff --git a/networksecurity/service/Android.bp b/networksecurity/service/Android.bp
index f27acb7..d7aacdb 100644
--- a/networksecurity/service/Android.bp
+++ b/networksecurity/service/Android.bp
@@ -24,12 +24,14 @@
 
     srcs: [
         "src/**/*.java",
+        ":statslog-certificate-transparency-java-gen",
     ],
 
     libs: [
         "framework-configinfrastructure.stubs.module_lib",
         "framework-connectivity-pre-jarjar",
         "service-connectivity-pre-jarjar",
+        "framework-statsd.stubs.module_lib",
     ],
 
     static_libs: [
@@ -49,3 +51,10 @@
     sdk_version: "system_server_current",
     apex_available: ["com.android.tethering"],
 }
+
+genrule {
+    name: "statslog-certificate-transparency-java-gen",
+    tools: ["stats-log-api-gen"],
+    cmd: "$(location stats-log-api-gen) --java $(out) --module certificate_transparency --javaPackage com.android.server.net.ct --javaClass CertificateTransparencyStatsLog",
+    out: ["com/android/server/net/ct/CertificateTransparencyStatsLog.java"],
+}
diff --git a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyDownloader.java b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyDownloader.java
index d16a760..79123ee 100644
--- a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyDownloader.java
+++ b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyDownloader.java
@@ -16,6 +16,15 @@
 
 package com.android.server.net.ct;
 
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_DEVICE_OFFLINE;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_DOWNLOAD_CANNOT_RESUME;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_HTTP_ERROR;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_NO_DISK_SPACE;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_UNKNOWN;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_TOO_MANY_REDIRECTS;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_VERSION_ALREADY_EXISTS;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__PENDING_WAITING_FOR_WIFI;
+
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import android.annotation.RequiresApi;
@@ -50,18 +59,21 @@
     private final DownloadHelper mDownloadHelper;
     private final SignatureVerifier mSignatureVerifier;
     private final CertificateTransparencyInstaller mInstaller;
+    private final CertificateTransparencyLogger mLogger;
 
     CertificateTransparencyDownloader(
             Context context,
             DataStore dataStore,
             DownloadHelper downloadHelper,
             SignatureVerifier signatureVerifier,
-            CertificateTransparencyInstaller installer) {
+            CertificateTransparencyInstaller installer,
+            CertificateTransparencyLogger logger) {
         mContext = context;
         mSignatureVerifier = signatureVerifier;
         mDataStore = dataStore;
         mDownloadHelper = downloadHelper;
         mInstaller = installer;
+        mLogger = logger;
     }
 
     void initialize() {
@@ -197,6 +209,8 @@
         }
         if (!success) {
             Log.w(TAG, "Log list did not pass verification");
+
+            // TODO(b/384931263): add logging for failed signature verification
             return;
         }
 
@@ -225,7 +239,10 @@
             mDataStore.store();
         } else {
             if (updateFailureCount()) {
-                // TODO(378626065): Report FAILURE_VERSION_ALREADY_EXISTS failure via statsd.
+                mLogger.logCTLogListUpdateFailedEvent(
+                        CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_VERSION_ALREADY_EXISTS,
+                        mDataStore.getPropertyInt(
+                            Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0));
             }
         }
     }
@@ -234,7 +251,46 @@
         Log.e(TAG, "Download failed with " + status);
 
         if (updateFailureCount()) {
-            // TODO(378626065): Report download failure via statsd.
+            int failureCount = mDataStore.getPropertyInt(
+                    Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0);
+
+            // HTTP Error
+            if (400 <= status.reason() && status.reason() <= 600) {
+                mLogger.logCTLogListUpdateFailedEvent(
+                        CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_HTTP_ERROR,
+                        failureCount,
+                        status.reason()
+                );
+            } else {
+                // TODO(b/384935059): handle blocked domain logging
+                // TODO(b/384936292): add additionalchecks for pending wifi status
+                mLogger.logCTLogListUpdateFailedEvent(
+                        downloadStatusToFailureReason(status.reason()),
+                        failureCount
+                );
+            }
+        }
+    }
+
+    /** Converts DownloadStatus reason into failure reason to log. */
+    private int downloadStatusToFailureReason(int downloadStatusReason) {
+        switch(downloadStatusReason) {
+            case DownloadManager.PAUSED_WAITING_TO_RETRY:
+            case DownloadManager.PAUSED_WAITING_FOR_NETWORK:
+                return CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_DEVICE_OFFLINE;
+            case DownloadManager.ERROR_UNHANDLED_HTTP_CODE:
+            case DownloadManager.ERROR_HTTP_DATA_ERROR:
+                return CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_HTTP_ERROR;
+            case DownloadManager.ERROR_TOO_MANY_REDIRECTS:
+                return CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_TOO_MANY_REDIRECTS;
+            case DownloadManager.ERROR_CANNOT_RESUME:
+                return CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_DOWNLOAD_CANNOT_RESUME;
+            case DownloadManager.ERROR_INSUFFICIENT_SPACE:
+                return CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_NO_DISK_SPACE;
+            case DownloadManager.PAUSED_QUEUED_FOR_WIFI:
+                return CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__PENDING_WAITING_FOR_WIFI;
+            default:
+                return CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_UNKNOWN;
         }
     }
 
@@ -253,7 +309,7 @@
 
         boolean shouldReport = new_failure_count >= Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD;
         if (shouldReport) {
-            Log.e(TAG,
+            Log.d(TAG,
                     "Log list update failure count exceeds threshold: " + new_failure_count);
         }
         return shouldReport;
diff --git a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyLogger.java b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyLogger.java
new file mode 100644
index 0000000..93493c2
--- /dev/null
+++ b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyLogger.java
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.net.ct;
+
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED;
+
+/** Helper class to interface with logging to statsd. */
+public class CertificateTransparencyLogger {
+
+    public CertificateTransparencyLogger() {}
+
+    /**
+     * Logs a CTLogListUpdateFailed event to statsd, when no HTTP error status code is present.
+     *
+     * @param failureReason reason why the log list wasn't updated (e.g. DownloadManager failures)
+     * @param failureCount number of consecutive log list update failures
+     */
+    public void logCTLogListUpdateFailedEvent(int failureReason, int failureCount) {
+        logCTLogListUpdateFailedEvent(failureReason, failureCount, /* httpErrorStatusCode= */ 0);
+    }
+
+    /**
+     * Logs a CTLogListUpdateFailed event to statsd, when an HTTP error status code is provided.
+     *
+     * @param failureReason reason why the log list wasn't updated (e.g. DownloadManager failures)
+     * @param failureCount number of consecutive log list update failures
+     * @param httpErrorStatusCode if relevant, the HTTP error status code from DownloadManager
+     */
+    public void logCTLogListUpdateFailedEvent(
+            int failureReason, int failureCount, int httpErrorStatusCode) {
+        CertificateTransparencyStatsLog.write(
+                CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED,
+                failureReason,
+                failureCount,
+                httpErrorStatusCode
+        );
+    }
+}
diff --git a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java
index 6151727..2a27204 100644
--- a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java
+++ b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java
@@ -59,7 +59,8 @@
                         dataStore,
                         downloadHelper,
                         signatureVerifier,
-                        new CertificateTransparencyInstaller());
+                        new CertificateTransparencyInstaller(),
+                        new CertificateTransparencyLogger());
         mFlagsListener =
                 new CertificateTransparencyFlagsListener(dataStore, signatureVerifier, downloader);
         mCertificateTransparencyJob =
diff --git a/networksecurity/tests/unit/src/com/android/server/net/ct/CertificateTransparencyDownloaderTest.java b/networksecurity/tests/unit/src/com/android/server/net/ct/CertificateTransparencyDownloaderTest.java
index 4748043..3a359f4 100644
--- a/networksecurity/tests/unit/src/com/android/server/net/ct/CertificateTransparencyDownloaderTest.java
+++ b/networksecurity/tests/unit/src/com/android/server/net/ct/CertificateTransparencyDownloaderTest.java
@@ -15,12 +15,17 @@
  */
 package com.android.server.net.ct;
 
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_NO_DISK_SPACE;
+import static com.android.server.net.ct.CertificateTransparencyStatsLog.CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_VERSION_ALREADY_EXISTS;
+
 import static com.google.common.truth.Truth.assertThat;
 
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -67,6 +72,7 @@
 
     @Mock private DownloadManager mDownloadManager;
     @Mock private CertificateTransparencyInstaller mCertificateTransparencyInstaller;
+    @Mock private CertificateTransparencyLogger mLogger;
 
     private PrivateKey mPrivateKey;
     private PublicKey mPublicKey;
@@ -96,7 +102,8 @@
                         mDataStore,
                         new DownloadHelper(mDownloadManager),
                         mSignatureVerifier,
-                        mCertificateTransparencyInstaller);
+                        mCertificateTransparencyInstaller,
+                        mLogger);
 
         prepareDataStore();
         prepareDownloadManager();
@@ -203,7 +210,10 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD);
-        // TODO(378626065): Verify logged failure via statsd.
+        verify(mLogger, times(1)).logCTLogListUpdateFailedEvent(
+                CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_NO_DISK_SPACE,
+                Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD
+        );
     }
 
     @Test
@@ -223,7 +233,7 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(1);
-        // TODO(378626065): Verify no failure logged via statsd.
+        verify(mLogger, never()).logCTLogListUpdateFailedEvent(anyInt(), anyInt());
     }
 
     @Test
@@ -274,7 +284,10 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD);
-        // TODO(378626065): Verify logged failure via statsd.
+        verify(mLogger, times(1)).logCTLogListUpdateFailedEvent(
+                CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_NO_DISK_SPACE,
+                Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD
+        );
     }
 
     @Test
@@ -295,7 +308,7 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(1);
-        // TODO(378626065): Verify no failure logged via statsd.
+        verify(mLogger, never()).logCTLogListUpdateFailedEvent(anyInt(), anyInt());
     }
 
     @Test
@@ -356,7 +369,10 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD);
-        // TODO(378626065): Verify logged failure via statsd.
+        verify(mLogger, times(1)).logCTLogListUpdateFailedEvent(
+                CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_NO_DISK_SPACE,
+                Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD
+        );
     }
 
     @Test
@@ -377,7 +393,7 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(1);
-        // TODO(378626065): Verify no failure logged via statsd.
+        verify(mLogger, never()).logCTLogListUpdateFailedEvent(anyInt(), anyInt());
     }
 
     @Test
@@ -425,7 +441,10 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD);
-        // TODO(378626065): Verify logged failure via statsd.
+        verify(mLogger, times(1)).logCTLogListUpdateFailedEvent(
+                CERTIFICATE_TRANSPARENCY_LOG_LIST_UPDATE_FAILED__FAILURE_REASON__FAILURE_VERSION_ALREADY_EXISTS,
+                Config.LOG_LIST_UPDATE_FAILURE_THRESHOLD
+        );
     }
 
     @Test
@@ -451,7 +470,7 @@
         assertThat(mDataStore.getPropertyInt(
                 Config.LOG_LIST_UPDATE_FAILURE_COUNT, /* defaultValue= */ 0))
                         .isEqualTo(1);
-        // TODO(378626065): Verify no failure logged via statsd.
+        verify(mLogger, never()).logCTLogListUpdateFailedEvent(anyInt(), anyInt());
     }
 
     @Test