diff --git a/server/src/db/migration/0008_backfillMonitorLastEvaluatedAt.ts b/server/src/db/migration/0008_backfillMonitorLastEvaluatedAt.ts
new file mode 100644
index 000000000..8f8de7308
--- /dev/null
+++ b/server/src/db/migration/0008_backfillMonitorLastEvaluatedAt.ts
@@ -0,0 +1,24 @@
+import { MonitorModel } from "../../domain/monitors/monitor.model.js";
+import { logger } from "@/utils/logger.js";
+
+/**
+ * Backfill lastEvaluatedAt on monitors created before the lastEvaluatedAt existed.
+ */
+export async function backfillMonitorLastEvaluatedAt(): Promise<void> {
+	const SERVICE_NAME = "Migration:BackfillMonitorLastEvaluatedAt";
+
+	try {
+		logger.info({ service: SERVICE_NAME, message: "Starting lastEvaluatedAt backfill" });
+
+		const result = await MonitorModel.updateMany({ lastEvaluatedAt: { $exists: false } }, { $set: { lastEvaluatedAt: 0 } });
+
+		logger.info({
+			service: SERVICE_NAME,
+			message: `Backfilled lastEvaluatedAt on ${result.modifiedCount} monitors`,
+		});
+	} catch (error) {
+		const errorMessage = error instanceof Error ? error.message : String(error);
+		logger.error({ service: SERVICE_NAME, message: `Error backfilling lastEvaluatedAt: ${errorMessage}` });
+		throw error;
+	}
+}
diff --git a/server/src/db/migration/index.ts b/server/src/db/migration/index.ts
index ac78cc813..d68a2468e 100644
--- a/server/src/db/migration/index.ts
+++ b/server/src/db/migration/index.ts
@@ -6,6 +6,7 @@ import MigrationModel from "../../domain/migrations/migration.model.js";
 import { migrateStatusPageTypeToArray } from "./0005_migrateStatusPageTypeToArray.js";
 import { cleanupDuplicateMonitorStatsForUniqueIndex } from "./0006_cleanupDuplicateMonitorStatsForUniqueIndex.js";
 import { migrateMaintenanceWindowMonitorIdToArray } from "./0007_migrateMaintenanceWindowMonitorIdToArray.js";
+import { backfillMonitorLastEvaluatedAt } from "./0008_backfillMonitorLastEvaluatedAt.js";
 import type { ILogger } from "@/utils/logger.js";
 
 type MigrationEntry = {
@@ -21,6 +22,7 @@ const migrations: MigrationEntry[] = [
 	{ name: "0005_migrateStatusPageTypeToArray", execute: migrateStatusPageTypeToArray },
 	{ name: "0006_cleanupDuplicateMonitorStatsForUniqueIndex", execute: cleanupDuplicateMonitorStatsForUniqueIndex },
 	{ name: "0007_migrateMaintenanceWindowMonitorIdToArray", execute: migrateMaintenanceWindowMonitorIdToArray },
+	{ name: "0008_backfillMonitorLastEvaluatedAt", execute: backfillMonitorLastEvaluatedAt },
 ];
 
 const runMigrations = async (logger?: ILogger) => {