--- a/toolkit/components/downloads/ApplicationReputation.cpp
+++ b/toolkit/components/downloads/ApplicationReputation.cpp
@@ -1023,16 +1023,18 @@ PendingLookup::SendRemoteQueryInternal()
   return NS_OK;
 }
 
 NS_IMETHODIMP
 PendingLookup::Notify(nsITimer* aTimer)
 {
   LOG(("Remote lookup timed out [this = %p]", this));
   MOZ_ASSERT(aTimer == mTimeoutTimer);
+  Accumulate(mozilla::Telemetry::APPLICATION_REPUTATION_REMOTE_LOOKUP_TIMEOUT,
+    true);
   mChannel->Cancel(NS_ERROR_NET_TIMEOUT);
   mTimeoutTimer->Cancel();
   return NS_OK;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 //// nsIStreamListener
 static NS_METHOD
@@ -1067,16 +1069,19 @@ PendingLookup::OnStartRequest(nsIRequest
 NS_IMETHODIMP
 PendingLookup::OnStopRequest(nsIRequest *aRequest,
                              nsISupports *aContext,
                              nsresult aResult) {
   NS_ENSURE_STATE(mCallback);
 
   bool shouldBlock = false;
   uint32_t verdict = nsIApplicationReputationService::VERDICT_SAFE;
+  Accumulate(mozilla::Telemetry::APPLICATION_REPUTATION_REMOTE_LOOKUP_TIMEOUT,
+    false);
+
   nsresult rv = OnStopRequestInternal(aRequest, aContext, aResult,
                                       &shouldBlock, &verdict);
   OnComplete(shouldBlock, rv, verdict);
   return rv;
 }
 
 nsresult
 PendingLookup::OnStopRequestInternal(nsIRequest *aRequest,

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -83,16 +83,23 @@
     "n_values": 8,
     "description": "Application reputation remote response (0=SAFE, 1=DANGEROUS, 2=UNCOMMON, 3=POTENTIALLY_UNWANTED, 4=DANGEROUS_HOST)"
   },
   "APPLICATION_REPUTATION_COUNT": {
     "expires_in_version": "never",
     "kind": "boolean",
     "description": "Application reputation query count (both local and remote)"
   },
+  "APPLICATION_REPUTATION_REMOTE_LOOKUP_TIMEOUT": {
+    "alert_emails": ["gcp@mozilla.com", "francois@mozilla.com"],
+    "expires_in_version": "55",
+    "kind": "boolean",
+    "bug_numbers": [1172689],
+    "description": "Recorded when application reputation remote lookup is performed, `true` is recorded if the lookup times out."
+  },
   "AUDIOSTREAM_FIRST_OPEN_MS": {
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 10000,
     "n_buckets": 50,
     "description": "The length of time (in milliseconds) for the first open of AudioStream."
   },
   "AUDIOSTREAM_LATER_OPEN_MS": {