diff --git a/server/src/controllers/controllerUtils.ts b/server/src/controllers/controllerUtils.ts
index 67dc71a70..74006c8dc 100755
--- a/server/src/controllers/controllerUtils.ts
+++ b/server/src/controllers/controllerUtils.ts
@@ -6,7 +6,9 @@ type SSLCheckerType = typeof sslChecker;
 export const fetchMonitorCertificate = async (checker: SSLCheckerType, monitor: Monitor): Promise<SSLDetails> => {
 	const monitorUrl = new URL(monitor.url);
 	const hostname = monitorUrl.hostname;
-	const cert = await checker(hostname);
+	const urlPort = monitorUrl.port ? Number(monitorUrl.port) : undefined;
+	const port = monitor.port ?? urlPort;
+	const cert = await checker(hostname, port ? { port } : undefined);
 	if (cert?.validTo === null || cert?.validTo === undefined) {
 		throw new Error("Certificate not found");
 	}
diff --git a/server/test/unit/controllers/controllerUtils.test.ts b/server/test/unit/controllers/controllerUtils.test.ts
new file mode 100644
index 000000000..96fd245e8
--- /dev/null
+++ b/server/test/unit/controllers/controllerUtils.test.ts
@@ -0,0 +1,55 @@
+import { describe, expect, it, jest } from "@jest/globals";
+import { fetchMonitorCertificate } from "../../../src/controllers/controllerUtils.ts";
+import type { Monitor } from "../../../src/types/index.ts";
+import type { SSLDetails } from "ssl-checker";
+
+const certificate: SSLDetails = {
+	daysRemaining: 30,
+	valid: true,
+	validFrom: "2026-01-01T00:00:00.000Z",
+	validTo: "2026-06-01T00:00:00.000Z",
+	validFor: ["checkmate.example.org"],
+};
+
+const makeMonitor = (overrides?: Partial<Monitor>): Monitor =>
+	({
+		id: "monitor-1",
+		teamId: "team-1",
+		url: "https://checkmate.example.org",
+		ignoreTlsErrors: false,
+		...overrides,
+	}) as Monitor;
+
+describe("controllerUtils", () => {
+	describe("fetchMonitorCertificate", () => {
+		it("checks the explicit HTTPS URL port when present", async () => {
+			const checker = jest.fn().mockResolvedValue(certificate);
+
+			await fetchMonitorCertificate(checker as any, makeMonitor({ url: "https://checkmate.example.org:54321/status" }));
+
+			expect(checker).toHaveBeenCalledWith("checkmate.example.org", { port: 54321 });
+		});
+
+		it("uses the monitor port when the URL does not include one", async () => {
+			const checker = jest.fn().mockResolvedValue(certificate);
+
+			await fetchMonitorCertificate(checker as any, makeMonitor({ url: "https://checkmate.example.org/status", port: 8443 }));
+
+			expect(checker).toHaveBeenCalledWith("checkmate.example.org", { port: 8443 });
+		});
+
+		it("keeps the previous default-port behavior when no port is configured", async () => {
+			const checker = jest.fn().mockResolvedValue(certificate);
+
+			await fetchMonitorCertificate(checker as any, makeMonitor());
+
+			expect(checker).toHaveBeenCalledWith("checkmate.example.org", undefined);
+		});
+
+		it("throws when no certificate expiry is returned", async () => {
+			const checker = jest.fn().mockResolvedValue({ ...certificate, validTo: undefined });
+
+			await expect(fetchMonitorCertificate(checker as any, makeMonitor())).rejects.toThrow("Certificate not found");
+		});
+	});
+});