diff --git a/src/modules/platform/business-calendars/controller/business-calendars.controller.ts b/src/modules/platform/business-calendars/controller/business-calendars.controller.ts
index 0882c84..8c7ae4e 100644
--- a/src/modules/platform/business-calendars/controller/business-calendars.controller.ts
+++ b/src/modules/platform/business-calendars/controller/business-calendars.controller.ts
@@ -22,7 +22,7 @@ export class BusinessCalendarsController {
 
   async getById(request: FastifyRequest, reply: FastifyReply) {
     const { id } = request.params as { id: string };
-    const calendar = await this.service.getById(id);
+    const calendar = await this.service.getByIdWithHolidays(id);
     return reply.status(200).send({ success: true, data: calendar, meta: null });
   }
 
diff --git a/src/modules/platform/business-calendars/service/business-calendars.service.ts b/src/modules/platform/business-calendars/service/business-calendars.service.ts
index cbc1bc8..835ab55 100644
--- a/src/modules/platform/business-calendars/service/business-calendars.service.ts
+++ b/src/modules/platform/business-calendars/service/business-calendars.service.ts
@@ -34,6 +34,14 @@ export class BusinessCalendarsService {
     return calendar;
   }
 
+  /** 012-admin-list-views follow-up: GET /admin/business-calendars/:id's own response — a
+   * calendar's holidays had no way to be read back at all before this (only added/removed). */
+  async getByIdWithHolidays(id: string): Promise<BusinessCalendar & { holidays: Holiday[] }> {
+    const calendar = await this.calendars.findByIdWithHolidays(id);
+    if (!calendar) throw new NotFoundError('Business calendar not found.');
+    return calendar;
+  }
+
   async list(): Promise<BusinessCalendar[]> {
     return this.calendars.findAll();
   }
diff --git a/tests/integration/business-calendars.test.ts b/tests/integration/business-calendars.test.ts
new file mode 100644
index 0000000..d661767
--- /dev/null
+++ b/tests/integration/business-calendars.test.ts
@@ -0,0 +1,60 @@
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { buildApp } from '@/app';
+import { prismaClient } from '@/infrastructure/database';
+import { FastifyInstance } from 'fastify';
+import { loginAs, authHeader } from '../helpers/auth';
+
+/**
+ * Covers specs/008-sla-escalation's business-calendar create/holiday flow, plus
+ * 012-admin-list-views' own follow-up: GET /admin/business-calendars/:id now includes holidays
+ * (previously only addable/removable, never readable back).
+ */
+describe('Business calendars — create, add a holiday, and read both back', () => {
+  let app: FastifyInstance;
+  let token: string;
+  let calendarId: string;
+
+  beforeAll(async () => {
+    app = await buildApp();
+    token = await loginAs(app, 'ADMIN');
+  });
+
+  afterAll(async () => {
+    await prismaClient.holiday.deleteMany({ where: { calendarId } });
+    await prismaClient.businessCalendar.deleteMany({ where: { id: calendarId } });
+    await app.close();
+  });
+
+  it('a created calendar and an added holiday are both displayed back exactly as entered', async () => {
+    const created = await app.inject({
+      method: 'POST',
+      url: '/admin/business-calendars',
+      headers: authHeader(token),
+      payload: {
+        name: `Test Calendar ${Date.now()}`,
+        timezone: 'America/New_York',
+        workingHours: { mon: { start: '09:00', end: '17:00' } },
+      },
+    });
+    expect(created.statusCode).toBe(201);
+    calendarId = created.json().data.id;
+
+    const holiday = await app.inject({
+      method: 'POST',
+      url: `/admin/business-calendars/${calendarId}/holidays`,
+      headers: authHeader(token),
+      payload: { date: '2026-12-25', description: 'Christmas' },
+    });
+    expect(holiday.statusCode).toBe(201);
+
+    const fetched = await app.inject({
+      method: 'GET',
+      url: `/admin/business-calendars/${calendarId}`,
+      headers: authHeader(token),
+    });
+    expect(fetched.statusCode).toBe(200);
+    expect(fetched.json().data.workingHours.mon).toEqual({ start: '09:00', end: '17:00' });
+    expect(fetched.json().data.holidays).toHaveLength(1);
+    expect(fetched.json().data.holidays[0].description).toBe('Christmas');
+  });
+});