diff --git a/browser/serp_metrics/profile_attributes_time_period_store.cc b/browser/serp_metrics/profile_attributes_time_period_store.cc
index 9ad09fdb7da..6a8c7ce93d3 100644
--- a/browser/serp_metrics/profile_attributes_time_period_store.cc
+++ b/browser/serp_metrics/profile_attributes_time_period_store.cc
@@ -14,12 +14,19 @@
 namespace serp_metrics {
 
 ProfileAttributesTimePeriodStore::ProfileAttributesTimePeriodStore(
-    const base::FilePath& profile_path,
+    base::FilePath profile_path,
     ProfileAttributesStorage& profile_attributes_storage,
     std::string_view metric_name)
-    : profile_path_(profile_path),
+    : profile_path_(std::move(profile_path)),
       profile_attributes_storage_(profile_attributes_storage),
-      metric_name_(metric_name) {}
+      metric_name_(metric_name) {
+  if (!Get()) {
+    // Initialize an empty list so the engine key always exists in the profile
+    // attributes dict. This ensures virtual pref paths that query this key
+    // resolve to 0 rather than failing on a clean profile.
+    Set(base::ListValue());
+  }
+}
 
 ProfileAttributesTimePeriodStore::~ProfileAttributesTimePeriodStore() = default;
 
@@ -46,9 +53,8 @@ void ProfileAttributesTimePeriodStore::Set(base::ListValue list) {
   }
 
   base::DictValue serp_metrics;
-  if (const base::DictValue* existing_serp_metrics = entry->GetSerpMetrics();
-      existing_serp_metrics) {
-    serp_metrics = existing_serp_metrics->Clone();
+  if (const base::DictValue* const value = entry->GetSerpMetrics()) {
+    serp_metrics = value->Clone();
   }
 
   serp_metrics.Set(metric_name_, std::move(list));
diff --git a/browser/serp_metrics/profile_attributes_time_period_store.h b/browser/serp_metrics/profile_attributes_time_period_store.h
index c65b8be6c2d..d7730cb07d6 100644
--- a/browser/serp_metrics/profile_attributes_time_period_store.h
+++ b/browser/serp_metrics/profile_attributes_time_period_store.h
@@ -32,7 +32,7 @@ class ProfileAttributesTimePeriodStore final
     : public SerpMetricsTimePeriodStore {
  public:
   ProfileAttributesTimePeriodStore(
-      const base::FilePath& profile_path,
+      base::FilePath profile_path,
       ProfileAttributesStorage& profile_attributes_storage,
       std::string_view metric_name);
 
diff --git a/browser/serp_metrics/profile_attributes_time_period_store_unittest.cc b/browser/serp_metrics/profile_attributes_time_period_store_unittest.cc
index e65b26f33d4..2f01c5ed89e 100644
--- a/browser/serp_metrics/profile_attributes_time_period_store_unittest.cc
+++ b/browser/serp_metrics/profile_attributes_time_period_store_unittest.cc
@@ -80,24 +80,26 @@ TEST_F(ProfileAttributesTimePeriodStoreTest, ClearStore) {
   EXPECT_FALSE(store.Get());
 }
 
-TEST_F(ProfileAttributesTimePeriodStoreTest, GetUninitializedStore) {
+TEST_F(ProfileAttributesTimePeriodStoreTest,
+       GetReturnsEmptyListOnCleanProfile) {
   ProfileAttributesTimePeriodStore store(
       profile_path(), profile_attributes_storage(), kMetricName);
-  EXPECT_FALSE(store.Get());
+  ASSERT_TRUE(store.Get());
+  EXPECT_TRUE(store.Get()->empty());
 }
 
 TEST_F(ProfileAttributesTimePeriodStoreTest, SetStoresWithDifferentKeys) {
-  ProfileAttributesTimePeriodStore store1(
+  ProfileAttributesTimePeriodStore store_1(
       profile_path(), profile_attributes_storage(), kMetricName);
-  ProfileAttributesTimePeriodStore store2(
+  ProfileAttributesTimePeriodStore store_2(
       profile_path(), profile_attributes_storage(), "other_testing_metric");
-  store1.Set(base::ListValue().Append(1));
-  store2.Set(base::ListValue().Append(2).Append(3));
+  store_1.Set(base::ListValue().Append(1));
+  store_2.Set(base::ListValue().Append(2).Append(3));
 
-  ASSERT_TRUE(store1.Get());
-  EXPECT_THAT(*store1.Get(), ::testing::ElementsAre(1));
-  ASSERT_TRUE(store2.Get());
-  EXPECT_THAT(*store2.Get(), ::testing::ElementsAre(2, 3));
+  ASSERT_TRUE(store_1.Get());
+  EXPECT_THAT(*store_1.Get(), ::testing::ElementsAre(1));
+  ASSERT_TRUE(store_2.Get());
+  EXPECT_THAT(*store_2.Get(), ::testing::ElementsAre(2, 3));
 }
 
 }  // namespace serp_metrics