diff --git a/backend/src/modules/staff/staff-working-hours.service.ts b/backend/src/modules/staff/staff-working-hours.service.ts
index 1fb9b1a..d7568a8 100644
--- a/backend/src/modules/staff/staff-working-hours.service.ts
+++ b/backend/src/modules/staff/staff-working-hours.service.ts
@@ -6,7 +6,9 @@ import {
 } from '@nestjs/common';
 import { PrismaService } from '../../../prisma/prisma.service';
 import {
+  appointmentWithinWorkingHours,
   blocksForDay,
+  localDayOfWeekMondayZero,
   validateWorkingHoursBlocks,
   type WorkingHoursBlockInput,
 } from '../../common/working-hours';
@@ -68,6 +70,11 @@ export class StaffWorkingHoursService {
     }
 
     const normalizedBlocks = this.normalizeBlocks(dto.blocks);
+    await this.assertNoConflictingAppointments(
+      organizationId,
+      membership.userId,
+      normalizedBlocks,
+    );
 
     await this.prisma.$transaction(async (tx) => {
       const schedule = await tx.staffWorkingHoursSchedule.upsert({
@@ -142,10 +149,66 @@ export class StaffWorkingHoursService {
     }));
   }
 
+  private async assertNoConflictingAppointments(
+    organizationId: string,
+    providerUserId: string,
+    blocks: WorkingHoursBlockInput[],
+  ) {
+    const now = new Date();
+    const appointments = await this.prisma.appointment.findMany({
+      where: {
+        organizationId,
+        providerUserId,
+        endAt: { gt: now },
+      },
+      include: {
+        patient: { select: { firstName: true, lastName: true } },
+      },
+      orderBy: { startAt: 'asc' },
+    });
+
+    const conflicts = appointments.filter((appointment) => {
+      const startAt = new Date(appointment.startAt);
+      const endAt = new Date(appointment.endAt);
+      const dayOfWeek = localDayOfWeekMondayZero(startAt.getDay());
+      const dayBlocks = blocksForDay(blocks, dayOfWeek);
+      if (dayBlocks.length === 0) {
+        return true;
+      }
+      return !appointmentWithinWorkingHours(startAt, endAt, dayBlocks);
+    });
+
+    if (conflicts.length === 0) {
+      return;
+    }
+
+    const examples = conflicts.slice(0, 3).map((appointment) => {
+      const startAt = new Date(appointment.startAt);
+      const patientName = `${appointment.patient.firstName} ${appointment.patient.lastName}`;
+      const when = startAt.toLocaleString(undefined, {
+        weekday: 'short',
+        month: 'short',
+        day: 'numeric',
+        hour: 'numeric',
+        minute: '2-digit',
+      });
+      return `${patientName} (${when})`;
+    });
+
+    const extra =
+      conflicts.length > examples.length
+        ? ` and ${conflicts.length - examples.length} more`
+        : '';
+
+    throw new BadRequestException(
+      `Cannot save working hours: ${conflicts.length} upcoming appointment${conflicts.length === 1 ? '' : 's'} fall outside the new schedule (${examples.join(', ')}${extra}). Reschedule or remove those appointments first.`,
+    );
+  }
+
   private async findMembership(membershipId: string, organizationId: string) {
     const membership = await this.prisma.membership.findFirst({
       where: { id: membershipId, organizationId },
-      select: { id: true, isOwner: true },
+      select: { id: true, isOwner: true, userId: true },
     });
     if (!membership) {
       throw new NotFoundException('Member not found');
diff --git a/frontend/src/app/(dashboard)/staff/page.tsx b/frontend/src/app/(dashboard)/staff/page.tsx
index e8f0a32..b305f65 100644
--- a/frontend/src/app/(dashboard)/staff/page.tsx
+++ b/frontend/src/app/(dashboard)/staff/page.tsx
@@ -416,11 +416,6 @@ export default function StaffPage() {
     setEditLoading(true);
     toast.setError('');
     try {
-      await staffApi.updateMember(editing.id, {
-        name: editName.trim(),
-        permissionNames: permissionNamesFromFeatureState(editPerms),
-      });
-
       if (editHasTreatmentEdit) {
         await staffApi.upsertWorkingHours(
           editing.id,
@@ -431,6 +426,11 @@ export default function StaffPage() {
         );
       }
 
+      await staffApi.updateMember(editing.id, {
+        name: editName.trim(),
+        permissionNames: permissionNamesFromFeatureState(editPerms),
+      });
+
       toast.showSuccess('Member updated.');
       setEditing(null);
       setEditStep(1);