diff --git a/server/src/db/migration/0007_migrateMaintenanceWindowMonitorIdToArray.ts b/server/src/db/migration/0007_migrateMaintenanceWindowMonitorIdToArray.ts
new file mode 100644
index 000000000..a60b8786a
--- /dev/null
+++ b/server/src/db/migration/0007_migrateMaintenanceWindowMonitorIdToArray.ts
@@ -0,0 +1,111 @@
+import mongoose from "mongoose";
+import type { AnyBulkWriteOperation, Document } from "mongodb";
+import { logger } from "@/utils/logger.js";
+import MaintenanceWindowModel from "../models/MaintenanceWindow.js";
+
+type GroupResult = {
+	_id: {
+		teamId: mongoose.Types.ObjectId;
+		name: string;
+		start: Date;
+		end: Date;
+		repeat: number;
+		durationUnit: string;
+		duration: number;
+		active: boolean;
+	};
+	docIds: mongoose.Types.ObjectId[];
+	monitorIds: mongoose.Types.ObjectId[];
+};
+
+export async function migrateMaintenanceWindowMonitorIdToArray(): Promise<void> {
+	const SERVICE_NAME = "Migration:MigrateMaintenanceWindowMonitorIdToArray";
+
+	try {
+		logger.info({
+			service: SERVICE_NAME,
+			message: "Starting migration of MaintenanceWindow.monitorId to monitorIds array (eager merge)",
+		});
+
+		const db = mongoose.connection.db;
+		if (!db) {
+			throw new Error("Database connection is not initialized");
+		}
+
+		// Group old-style docs by their scheduling key.
+		// Skip rows that already have a monitorIds array — those are either already migrated
+		// or in a partially-migrated state that needs manual review.
+		const groups: GroupResult[] = await MaintenanceWindowModel.aggregate<GroupResult>([
+			{
+				$match: {
+					monitorId: { $exists: true, $ne: null },
+					monitorIds: { $exists: false },
+				},
+			},
+			{
+				$group: {
+					_id: {
+						teamId: "$teamId",
+						name: "$name",
+						start: "$start",
+						end: "$end",
+						repeat: "$repeat",
+						durationUnit: "$durationUnit",
+						duration: "$duration",
+						active: "$active",
+					},
+					docIds: { $push: "$_id" },
+					monitorIds: { $addToSet: "$monitorId" },
+				},
+			},
+		]);
+
+		if (groups.length === 0) {
+			logger.info({ service: SERVICE_NAME, message: "No MaintenanceWindow documents needed migration" });
+			return;
+		}
+
+		const bulkOps: AnyBulkWriteOperation<Document>[] = [];
+		let originalDocCount = 0;
+
+		for (const group of groups) {
+			const { docIds, monitorIds } = group;
+			originalDocCount += docIds.length;
+			const [survivorId, ...duplicateIds] = docIds;
+
+			bulkOps.push({
+				updateOne: {
+					filter: { _id: survivorId },
+					update: {
+						$set: { monitorIds },
+						$unset: { monitorId: "" },
+					},
+				},
+			});
+
+			if (duplicateIds.length > 0) {
+				bulkOps.push({
+					deleteMany: {
+						filter: { _id: { $in: duplicateIds } },
+					},
+				});
+			}
+		}
+
+		const result = await MaintenanceWindowModel.collection.bulkWrite(bulkOps, { ordered: true });
+		const deletedCount = originalDocCount - groups.length;
+
+		logger.info({
+			service: SERVICE_NAME,
+			message: `Migration complete. Consolidated ${originalDocCount} old document(s) into ${groups.length} group window(s); deleted ${deletedCount} duplicate(s).`,
+		});
+		logger.debug({
+			service: SERVICE_NAME,
+			message: `bulkWrite result: modified=${result.modifiedCount}, deleted=${result.deletedCount}`,
+		});
+	} catch (error) {
+		const errorMessage = error instanceof Error ? error.message : String(error);
+		logger.error({ service: SERVICE_NAME, message: `Error during MaintenanceWindow migration: ${errorMessage}` });
+		throw error;
+	}
+}
diff --git a/server/src/db/migration/index.ts b/server/src/db/migration/index.ts
index 5b74a96fc..61785118e 100644
--- a/server/src/db/migration/index.ts
+++ b/server/src/db/migration/index.ts
@@ -5,6 +5,7 @@ import { fixInfrastructureThresholds } from "./0004_fixInfrastructureThresholds.
 import MigrationModel from "../models/Migration.js";
 import { migrateStatusPageTypeToArray } from "./0005_migrateStatusPageTypeToArray.js";
 import { cleanupDuplicateMonitorStatsForUniqueIndex } from "./0006_cleanupDuplicateMonitorStatsForUniqueIndex.js";
+import { migrateMaintenanceWindowMonitorIdToArray } from "./0007_migrateMaintenanceWindowMonitorIdToArray.js";
 import type { ILogger } from "@/utils/logger.js";
 
 type MigrationEntry = {
@@ -19,6 +20,7 @@ const migrations: MigrationEntry[] = [
 	{ name: "0004_fixInfrastructureThresholds", execute: fixInfrastructureThresholds },
 	{ name: "0005_migrateStatusPageTypeToArray", execute: migrateStatusPageTypeToArray },
 	{ name: "0006_cleanupDuplicateMonitorStatsForUniqueIndex", execute: cleanupDuplicateMonitorStatsForUniqueIndex },
+	{ name: "0007_migrateMaintenanceWindowMonitorIdToArray", execute: migrateMaintenanceWindowMonitorIdToArray },
 ];
 
 const runMigrations = async (logger?: ILogger) => {
diff --git a/server/src/db/models/MaintenanceWindow.ts b/server/src/db/models/MaintenanceWindow.ts
index 703c144c8..654ae50dd 100644
--- a/server/src/db/models/MaintenanceWindow.ts
+++ b/server/src/db/models/MaintenanceWindow.ts
@@ -1,8 +1,8 @@
 import { Schema, model, type Types } from "mongoose";
 import { DurationUnits, type MaintenanceWindow } from "@/types/maintenanceWindow.js";
 
-type MaintenanceWindowDocumentBase = Omit<MaintenanceWindow, "id" | "monitorId" | "teamId" | "start" | "end" | "createdAt" | "updatedAt"> & {
-	monitorId: Types.ObjectId;
+type MaintenanceWindowDocumentBase = Omit<MaintenanceWindow, "id" | "monitorIds" | "teamId" | "start" | "end" | "createdAt" | "updatedAt"> & {
+	monitorIds: Types.ObjectId[];
 	teamId: Types.ObjectId;
 	start: Date;
 	end: Date;
@@ -17,10 +17,10 @@ interface MaintenanceWindowDocument extends MaintenanceWindowDocumentBase {
 
 const MaintenanceWindowSchema = new Schema<MaintenanceWindowDocument>(
 	{
-		monitorId: {
-			type: Schema.Types.ObjectId,
+		monitorIds: {
+			type: [Schema.Types.ObjectId],
 			ref: "Monitor",
-			immutable: true,
+			index: true,
 		},
 		teamId: {
 			type: Schema.Types.ObjectId,
diff --git a/server/src/repositories/maintenance-windows/MongoMaintenanceWindowsRepository.ts b/server/src/repositories/maintenance-windows/MongoMaintenanceWindowsRepository.ts
index ad96328c5..635ddc2de 100644
--- a/server/src/repositories/maintenance-windows/MongoMaintenanceWindowsRepository.ts
+++ b/server/src/repositories/maintenance-windows/MongoMaintenanceWindowsRepository.ts
@@ -29,7 +29,7 @@ class MongoMaintenanceWindowsRepository implements IMaintenanceWindowsRepository
 	private toEntity = (doc: MaintenanceWindowDocument): MaintenanceWindow => {
 		return {
 			id: this.toStringId(doc._id),
-			monitorId: this.toStringId(doc.monitorId),
+			monitorIds: doc.monitorIds.map(this.toStringId),
 			teamId: this.toStringId(doc.teamId),
 			active: doc.active,
 			name: doc.name,
@@ -67,7 +67,7 @@ class MongoMaintenanceWindowsRepository implements IMaintenanceWindowsRepository
 
 	findByMonitorId = async (monitorId: string, teamId: string): Promise<MaintenanceWindow[]> => {
 		const maintenanceWindows = await MaintenanceWindowModel.find({
-			monitorId: monitorId,
+			monitorIds: monitorId,
 			teamId: teamId,
 		});
 		return this.mapDocuments(maintenanceWindows);
diff --git a/server/src/service/business/maintenanceWindowService.ts b/server/src/service/business/maintenanceWindowService.ts
index 50278d215..e56ad3757 100644
--- a/server/src/service/business/maintenanceWindowService.ts
+++ b/server/src/service/business/maintenanceWindowService.ts
@@ -27,7 +27,11 @@ export interface IMaintenanceWindowService {
 	}): Promise<{ maintenanceWindows: MaintenanceWindow[]; maintenanceWindowCount: number }>;
 	getMaintenanceWindowsByMonitorId(params: { monitorId: string; teamId: string }): Promise<MaintenanceWindow[]>;
 	deleteMaintenanceWindow(params: { id: string; teamId: string }): Promise<MaintenanceWindow>;
-	editMaintenanceWindow(params: { id: string; teamId: string; body: Partial<MaintenanceWindow> }): Promise<MaintenanceWindow>;
+	editMaintenanceWindow(params: {
+		id: string;
+		teamId: string;
+		body: Partial<Omit<MaintenanceWindow, "monitorIds">> & { monitors?: string[] };
+	}): Promise<MaintenanceWindow>;
 }
 
 export class MaintenanceWindowService implements IMaintenanceWindowService {
@@ -84,20 +88,17 @@ export class MaintenanceWindowService implements IMaintenanceWindowService {
 			});
 		}
 
-		const dbTransactions = monitorIDs.map((monitorId: string) => {
-			return this.maintenanceWindowsRepository.create({
-				teamId,
-				monitorId,
-				name: name,
-				active: active,
-				duration: duration,
-				durationUnit: durationUnit,
-				repeat: repeat,
-				start: start,
-				end: end,
-			});
+		await this.maintenanceWindowsRepository.create({
+			teamId,
+			monitorIds: monitorIDs,
+			name: name,
+			active: active,
+			duration: duration,
+			durationUnit: durationUnit,
+			repeat: repeat,
+			start: start,
+			end: end,
 		});
-		await Promise.all(dbTransactions);
 	};
 
 	getMaintenanceWindowById = async ({ id, teamId }: { id: string; teamId: string }) => {
@@ -135,7 +136,32 @@ export class MaintenanceWindowService implements IMaintenanceWindowService {
 		return await this.maintenanceWindowsRepository.deleteById(id, teamId);
 	};
 
-	editMaintenanceWindow = async ({ id, teamId, body }: { id: string; teamId: string; body: Partial<MaintenanceWindow> }) => {
-		return await this.maintenanceWindowsRepository.updateById(id, teamId, body);
+	editMaintenanceWindow = async ({
+		id,
+		teamId,
+		body,
+	}: {
+		id: string;
+		teamId: string;
+		body: Partial<Omit<MaintenanceWindow, "monitorIds">> & { monitors?: string[] };
+	}) => {
+		const { monitors, ...rest } = body;
+		const update: Partial<MaintenanceWindow> = rest;
+
+		if (monitors !== undefined) {
+			const monitorDocs = await this.monitorsRepository.findByIds(monitors);
+			const unauthorizedMonitors = monitorDocs.filter((monitor) => monitor.teamId !== teamId);
+			if (unauthorizedMonitors.length > 0) {
+				throw new AppError({
+					message: "Unauthorized to edit maintenance window for one or more monitors",
+					service: SERVICE_NAME,
+					method: "editMaintenanceWindow",
+					status: 403,
+				});
+			}
+			update.monitorIds = monitors;
+		}
+
+		return await this.maintenanceWindowsRepository.updateById(id, teamId, update);
 	};
 }
diff --git a/server/src/types/maintenanceWindow.ts b/server/src/types/maintenanceWindow.ts
index 950dc1713..4fc446dda 100644
--- a/server/src/types/maintenanceWindow.ts
+++ b/server/src/types/maintenanceWindow.ts
@@ -3,7 +3,7 @@ export type DurationUnit = (typeof DurationUnits)[number];
 
 export interface MaintenanceWindow {
 	id: string;
-	monitorId: string;
+	monitorIds: string[];
 	teamId: string;
 	active: boolean;
 	name: string;
diff --git a/server/src/validation/maintenanceWindowValidation.ts b/server/src/validation/maintenanceWindowValidation.ts
index c53e39b20..837db28e8 100644
--- a/server/src/validation/maintenanceWindowValidation.ts
+++ b/server/src/validation/maintenanceWindowValidation.ts
@@ -72,7 +72,7 @@ export const editMaintenanceByIdWindowBodyValidation = z
 		start: dateToString.optional(),
 		end: dateToString.optional(),
 		expiry: dateToString.optional(),
-		monitors: z.array(z.string()).optional(),
+		monitors: z.array(z.string()).min(1, "At least one monitor is required").optional(),
 		duration: z.number().optional(),
 		durationUnit: z.enum(DurationUnits).optional(),
 	})
diff --git a/server/test/integration/heartbeatJobMaintenance.test.ts b/server/test/integration/heartbeatJobMaintenance.test.ts
index 663c2e61e..5df287242 100644
--- a/server/test/integration/heartbeatJobMaintenance.test.ts
+++ b/server/test/integration/heartbeatJobMaintenance.test.ts
@@ -8,7 +8,7 @@ const makeMaintenanceWindow = (overrides?: Partial<MaintenanceWindow>): Maintena
 	const end = new Date(now.getTime() + 60 * 60 * 1000); // 1 hour from now
 	return {
 		id: "mw-1",
-		monitorId: "mon-1",
+		monitorIds: ["mon-1"],
 		teamId: "team-1",
 		active: true,
 		name: "Test Maintenance",
@@ -109,6 +109,23 @@ describe("Heartbeat job: maintenance windows", () => {
 		expect(h.bufferStub.addToBuffer).toHaveBeenCalledTimes(1);
 	});
 
+	it("skips checks for every monitor covered by a group window", async () => {
+		const monitorA = makeMonitor({ id: "mon-a", name: "Monitor A" });
+		const monitorB = makeMonitor({ id: "mon-b", name: "Monitor B" });
+		h.monitorsRepo.seed(monitorA);
+		h.monitorsRepo.seed(monitorB);
+
+		// A single group window covers both monitors
+		h.maintenanceWindowsRepo.findByMonitorId.mockResolvedValue([makeMaintenanceWindow({ monitorIds: ["mon-a", "mon-b"] })]);
+
+		await h.heartbeatJob(monitorA);
+		await h.heartbeatJob(monitorB);
+
+		expect((await h.monitorsRepo.findById("mon-a", "team-1")).status).toBe("maintenance");
+		expect((await h.monitorsRepo.findById("mon-b", "team-1")).status).toBe("maintenance");
+		expect(h.networkService.requestStatus).not.toHaveBeenCalled();
+	});
+
 	it("skips checks when window is in the past (expired)", async () => {
 		const monitor = makeMonitor();
 		h.monitorsRepo.seed(monitor);
diff --git a/server/test/unit/services/maintenanceWindowService.test.ts b/server/test/unit/services/maintenanceWindowService.test.ts
index 302ff128c..5ce64238a 100644
--- a/server/test/unit/services/maintenanceWindowService.test.ts
+++ b/server/test/unit/services/maintenanceWindowService.test.ts
@@ -37,7 +37,7 @@ const createService = (overrides?: {
 
 const makeWindow = (overrides?: Partial<MaintenanceWindow>): MaintenanceWindow => ({
 	id: "mw-1",
-	monitorId: "mon-1",
+	monitorIds: ["mon-1"],
 	teamId: "team-1",
 	active: true,
 	name: "Scheduled Maintenance",
@@ -80,16 +80,16 @@ describe("MaintenanceWindowService", () => {
 	// ── createMaintenanceWindow ──────────────────────────────────────────────
 
 	describe("createMaintenanceWindow", () => {
-		it("creates a maintenance window for each monitor", async () => {
+		it("creates a single maintenance window covering all monitor IDs", async () => {
 			const { service, maintenanceWindowsRepository } = createService();
 
 			await service.createMaintenanceWindow(defaultCreateParams);
 
-			expect(maintenanceWindowsRepository.create).toHaveBeenCalledTimes(2);
+			expect(maintenanceWindowsRepository.create).toHaveBeenCalledTimes(1);
 			expect(maintenanceWindowsRepository.create).toHaveBeenCalledWith(
 				expect.objectContaining({
 					teamId: "team-1",
-					monitorId: "mon-1",
+					monitorIds: ["mon-1", "mon-2"],
 					name: "Scheduled Maintenance",
 					active: true,
 					duration: 60,
@@ -99,7 +99,6 @@ describe("MaintenanceWindowService", () => {
 					end: "2026-04-10T03:00:00Z",
 				})
 			);
-			expect(maintenanceWindowsRepository.create).toHaveBeenCalledWith(expect.objectContaining({ monitorId: "mon-2" }));
 		});
 
 		it("verifies monitor ownership via findByIds", async () => {
@@ -130,12 +129,13 @@ describe("MaintenanceWindowService", () => {
 			await expect(service.createMaintenanceWindow(defaultCreateParams)).resolves.toBeUndefined();
 		});
 
-		it("creates a single window when monitorIDs has one entry", async () => {
+		it("passes a single-element monitorIds array when only one monitor is provided", async () => {
 			const { service, maintenanceWindowsRepository } = createService();
 
 			await service.createMaintenanceWindow({ ...defaultCreateParams, monitorIDs: ["mon-1"] });
 
 			expect(maintenanceWindowsRepository.create).toHaveBeenCalledTimes(1);
+			expect(maintenanceWindowsRepository.create).toHaveBeenCalledWith(expect.objectContaining({ monitorIds: ["mon-1"] }));
 		});
 	});
 
@@ -248,5 +248,59 @@ describe("MaintenanceWindowService", () => {
 
 			expect(maintenanceWindowsRepository.updateById).toHaveBeenCalledWith("mw-1", "team-1", { active: false, repeat: 3600000 });
 		});
+
+		it("maps the monitors body field to monitorIds when calling the repository", async () => {
+			const { service, maintenanceWindowsRepository } = createService();
+
+			await service.editMaintenanceWindow({
+				id: "mw-1",
+				teamId: "team-1",
+				body: { monitors: ["mon-1", "mon-2"] },
+			});
+
+			expect(maintenanceWindowsRepository.updateById).toHaveBeenCalledWith("mw-1", "team-1", { monitorIds: ["mon-1", "mon-2"] });
+		});
+
+		it("verifies monitor ownership when monitors is in the body", async () => {
+			const { service, monitorsRepository } = createService();
+
+			await service.editMaintenanceWindow({
+				id: "mw-1",
+				teamId: "team-1",
+				body: { monitors: ["mon-1", "mon-2"] },
+			});
+
+			expect(monitorsRepository.findByIds).toHaveBeenCalledWith(["mon-1", "mon-2"]);
+		});
+
+		it("throws 403 when a new monitor belongs to a different team", async () => {
+			const monitorsRepository = createMonitorsRepo();
+			(monitorsRepository.findByIds as jest.Mock).mockResolvedValue([
+				{ id: "mon-1", teamId: "team-1" },
+				{ id: "mon-2", teamId: "team-other" },
+			]);
+			const { service, maintenanceWindowsRepository } = createService({ monitorsRepository });
+
+			await expect(
+				service.editMaintenanceWindow({
+					id: "mw-1",
+					teamId: "team-1",
+					body: { monitors: ["mon-1", "mon-2"] },
+				})
+			).rejects.toThrow("Unauthorized to edit maintenance window for one or more monitors");
+			expect(maintenanceWindowsRepository.updateById).not.toHaveBeenCalled();
+		});
+
+		it("does not call findByIds when monitors is not in the body", async () => {
+			const { service, monitorsRepository } = createService();
+
+			await service.editMaintenanceWindow({
+				id: "mw-1",
+				teamId: "team-1",
+				body: { name: "Updated Name" },
+			});
+
+			expect(monitorsRepository.findByIds).not.toHaveBeenCalled();
+		});
 	});
 });
diff --git a/server/test/unit/validation/maintenanceWindowValidation.test.ts b/server/test/unit/validation/maintenanceWindowValidation.test.ts
index dfede3670..a209ba64f 100644
--- a/server/test/unit/validation/maintenanceWindowValidation.test.ts
+++ b/server/test/unit/validation/maintenanceWindowValidation.test.ts
@@ -168,4 +168,24 @@ describe("editMaintenanceByIdWindowBodyValidation", () => {
 		});
 		expect(result.success).toBe(true);
 	});
+
+	it("accepts a body without a monitors field (monitors is optional on edit)", () => {
+		const result = editMaintenanceByIdWindowBodyValidation.safeParse({ name: "Updated Name" });
+		expect(result.success).toBe(true);
+	});
+
+	it("accepts a body with one or more monitors", () => {
+		const result = editMaintenanceByIdWindowBodyValidation.safeParse({ monitors: ["mon-1"] });
+		expect(result.success).toBe(true);
+	});
+
+	it("rejects an empty monitors array", () => {
+		const result = editMaintenanceByIdWindowBodyValidation.safeParse({ monitors: [] });
+		expect(result.success).toBe(false);
+		if (!result.success) {
+			expect(result.error.issues).toEqual(
+				expect.arrayContaining([expect.objectContaining({ message: "At least one monitor is required", path: ["monitors"] })])
+			);
+		}
+	});
 });