diff --git a/apps/api/src/integration/alarm-handlers.test.ts b/apps/api/src/integration/alarm-handlers.test.ts
new file mode 100644
index 000000000..1c3af46a8
--- /dev/null
+++ b/apps/api/src/integration/alarm-handlers.test.ts
@@ -0,0 +1,117 @@
+import "@databuddy/test/env";
+
+import { appRouter, type Context } from "@databuddy/rpc";
+import {
+	addToOrganization,
+	cleanup,
+	expectCode,
+	hasTestDb,
+	insertOrganization,
+	insertWebsite,
+	reset,
+	signUp,
+	userContext,
+} from "@databuddy/test";
+import { createProcedureClient } from "@orpc/server";
+import { afterAll, beforeEach, describe, expect, it } from "vitest";
+
+const iit = hasTestDb ? it : it.skip;
+
+beforeEach(() => reset());
+afterAll(() => cleanup());
+
+async function workspace() {
+	const user = await signUp();
+	const [org, foreignOrg] = await Promise.all([
+		insertOrganization(),
+		insertOrganization(),
+	]);
+	if (!(org && foreignOrg)) {
+		throw new Error("Organization insert returned no row");
+	}
+	await addToOrganization(user.id, org.id, "owner");
+	const [website, foreignWebsite] = await Promise.all([
+		insertWebsite({ organizationId: org.id }),
+		insertWebsite({ organizationId: foreignOrg.id }),
+	]);
+	if (!(website && foreignWebsite)) {
+		throw new Error("Website insert returned no row");
+	}
+	return { context: userContext(user, org.id), org, website, foreignWebsite };
+}
+
+function createAlarm(
+	context: Context,
+	organizationId: string,
+	websiteId?: string
+) {
+	return createProcedureClient(appRouter.alarms.create, { context })({
+		organizationId,
+		websiteId,
+		name: "Uptime alert",
+		triggerType: "uptime",
+		triggerConditions: {},
+		destinations: [
+			{ type: "email", identifier: "owner@example.com", config: {} },
+		],
+	});
+}
+
+describe("alarms website ownership", () => {
+	iit("rejects a website from another organization on create", async () => {
+		const { context, org, foreignWebsite } = await workspace();
+
+		await expectCode(
+			createAlarm(context, org.id, foreignWebsite.id),
+			"NOT_FOUND"
+		);
+	});
+
+	iit("rejects a deleted website on create", async () => {
+		const { context, org } = await workspace();
+		const deleted = await insertWebsite({
+			organizationId: org.id,
+			deletedAt: new Date(),
+		});
+		if (!deleted) {
+			throw new Error("Website insert returned no row");
+		}
+
+		await expectCode(createAlarm(context, org.id, deleted.id), "NOT_FOUND");
+	});
+
+	iit("links a website owned by the organization", async () => {
+		const { context, org, website } = await workspace();
+
+		const alarm = await createAlarm(context, org.id, website.id);
+
+		expect(alarm.websiteId).toBe(website.id);
+	});
+
+	iit("creates an organization-wide alarm without a website", async () => {
+		const { context, org } = await workspace();
+
+		const alarm = await createAlarm(context, org.id);
+
+		expect(alarm.websiteId).toBeNull();
+	});
+
+	iit(
+		"rejects moving an alarm to a foreign website but allows unlinking",
+		async () => {
+			const { context, org, website, foreignWebsite } = await workspace();
+			const alarm = await createAlarm(context, org.id, website.id);
+			const update = createProcedureClient(appRouter.alarms.update, {
+				context,
+			});
+
+			await expectCode(
+				update({ alarmId: alarm.id, websiteId: foreignWebsite.id }),
+				"NOT_FOUND"
+			);
+
+			const unlinked = await update({ alarmId: alarm.id, websiteId: null });
+			expect(unlinked.websiteId).toBeNull();
+		}
+	);
+});
diff --git a/packages/rpc/src/routers/alarms.ts b/packages/rpc/src/routers/alarms.ts
index e06f6250d..92939278e 100644
--- a/packages/rpc/src/routers/alarms.ts
+++ b/packages/rpc/src/routers/alarms.ts
@@ -1,8 +1,9 @@
-import { db, eq, withTransaction } from "@databuddy/db";
+import { and, db, eq, isNull, withTransaction } from "@databuddy/db";
 import {
 	alarmDestinations,
 	alarms,
 	alarmTriggerTypeValues,
+	websites,
 } from "@databuddy/db/schema";
 import { MAX_ALARM_DESTINATIONS } from "@databuddy/notifications";
 import { ratelimit } from "@databuddy/redis/rate-limit";
@@ -158,6 +159,26 @@ async function callerCanReadSecrets(
 	}
 }
 
+async function requireAlarmWebsite(
+	ctx: Context,
+	organizationId: string,
+	websiteId: string
+): Promise<void> {
+	const ownedWebsites = await ctx.db
+		.select({ id: websites.id })
+		.from(websites)
+		.where(
+			and(
+				eq(websites.id, websiteId),
+				eq(websites.organizationId, organizationId),
+				isNull(websites.deletedAt)
+			)
+		);
+	if (ownedWebsites.length === 0) {
+		throw rpcError.notFound("Website", websiteId);
+	}
+}
+
 export const alarmsRouter = {
 	list: protectedProcedure
 		.route({
@@ -228,6 +249,13 @@ export const alarmsRouter = {
 				resource: "organization",
 				permissions: ["update"],
 			});
+			if (input.websiteId) {
+				await requireAlarmWebsite(
+					context,
+					input.organizationId,
+					input.websiteId
+				);
+			}
 
 			const alarmId = randomUUIDv7();
 			const now = new Date();
@@ -293,11 +321,18 @@ export const alarmsRouter = {
 		)
 		.output(alarmOutputSchema)
 		.handler(async ({ context, input }) => {
-			await withResource(context, {
+			const alarm = await withResource(context, {
 				resource: "alarm",
 				id: input.alarmId,
 				permissions: ["update"],
 			});
+			if (input.websiteId) {
+				await requireAlarmWebsite(
+					context,
+					alarm.organizationId,
+					input.websiteId
+				);
+			}
 			const now = new Date();
 
 			const { alarmId, destinations, ...fields } = input;