diff --git a/tests/conftest.py b/tests/conftest.py
index 4a70e041..e84c0741 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -128,5 +128,6 @@ pytest_plugins = [
     "tests.fixtures.vendor_fixtures",
     "tests.fixtures.customer_fixtures",
     "tests.fixtures.marketplace_import_job_fixtures",
+    "tests.fixtures.message_fixtures",
     "tests.fixtures.testing_fixtures",
 ]
diff --git a/tests/unit/services/test_admin_customer_service.py b/tests/unit/services/test_admin_customer_service.py
new file mode 100644
index 00000000..0dd4ec76
--- /dev/null
+++ b/tests/unit/services/test_admin_customer_service.py
@@ -0,0 +1,280 @@
+# tests/unit/services/test_admin_customer_service.py
+"""
+Unit tests for AdminCustomerService.
+"""
+
+from decimal import Decimal
+
+import pytest
+
+from app.exceptions.customer import CustomerNotFoundException
+from app.services.admin_customer_service import AdminCustomerService
+from models.database.customer import Customer
+
+
+@pytest.fixture
+def admin_customer_service():
+    """Create AdminCustomerService instance."""
+    return AdminCustomerService()
+
+
+@pytest.fixture
+def customer_with_orders(db, test_vendor, test_customer):
+    """Create a customer with order data."""
+    test_customer.total_orders = 5
+    test_customer.total_spent = Decimal("250.00")
+    db.commit()
+    db.refresh(test_customer)
+    return test_customer
+
+
+@pytest.fixture
+def multiple_customers(db, test_vendor):
+    """Create multiple customers for testing."""
+    customers = []
+    for i in range(5):
+        customer = Customer(
+            vendor_id=test_vendor.id,
+            email=f"customer{i}@example.com",
+            hashed_password="hashed_password_placeholder",
+            first_name=f"First{i}",
+            last_name=f"Last{i}",
+            customer_number=f"CUST-00{i}",
+            is_active=(i % 2 == 0),  # Alternate active/inactive
+            total_orders=i,
+            total_spent=Decimal(str(i * 100)),
+        )
+        db.add(customer)
+        customers.append(customer)
+
+    db.commit()
+    for c in customers:
+        db.refresh(c)
+
+    return customers
+
+
+@pytest.mark.unit
+class TestAdminCustomerServiceList:
+    """Tests for list_customers method."""
+
+    def test_list_customers_empty(self, db, admin_customer_service, test_vendor):
+        """Test listing customers when none exist."""
+        customers, total = admin_customer_service.list_customers(db)
+
+        assert customers == []
+        assert total == 0
+
+    def test_list_customers_basic(self, db, admin_customer_service, test_customer):
+        """Test basic customer listing."""
+        customers, total = admin_customer_service.list_customers(db)
+
+        assert total == 1
+        assert len(customers) == 1
+        assert customers[0]["id"] == test_customer.id
+        assert customers[0]["email"] == test_customer.email
+
+    def test_list_customers_with_vendor_info(
+        self, db, admin_customer_service, test_customer, test_vendor
+    ):
+        """Test that vendor info is included."""
+        customers, total = admin_customer_service.list_customers(db)
+
+        assert customers[0]["vendor_name"] == test_vendor.name
+        assert customers[0]["vendor_code"] == test_vendor.vendor_code
+
+    def test_list_customers_filter_by_vendor(
+        self, db, admin_customer_service, multiple_customers, test_vendor
+    ):
+        """Test filtering by vendor ID."""
+        customers, total = admin_customer_service.list_customers(
+            db, vendor_id=test_vendor.id
+        )
+
+        assert total == 5
+        for customer in customers:
+            assert customer["vendor_id"] == test_vendor.id
+
+    def test_list_customers_filter_by_active_status(
+        self, db, admin_customer_service, multiple_customers
+    ):
+        """Test filtering by active status."""
+        # Get active customers (0, 2, 4 = 3 customers)
+        customers, total = admin_customer_service.list_customers(db, is_active=True)
+        assert total == 3
+
+        # Get inactive customers (1, 3 = 2 customers)
+        customers, total = admin_customer_service.list_customers(db, is_active=False)
+        assert total == 2
+
+    def test_list_customers_search_by_email(
+        self, db, admin_customer_service, multiple_customers
+    ):
+        """Test searching by email."""
+        customers, total = admin_customer_service.list_customers(
+            db, search="customer2@"
+        )
+
+        assert total == 1
+        assert customers[0]["email"] == "customer2@example.com"
+
+    def test_list_customers_search_by_name(
+        self, db, admin_customer_service, multiple_customers
+    ):
+        """Test searching by name."""
+        customers, total = admin_customer_service.list_customers(db, search="First3")
+
+        assert total == 1
+        assert customers[0]["first_name"] == "First3"
+
+    def test_list_customers_search_by_customer_number(
+        self, db, admin_customer_service, multiple_customers
+    ):
+        """Test searching by customer number."""
+        customers, total = admin_customer_service.list_customers(db, search="CUST-001")
+
+        assert total == 1
+        assert customers[0]["customer_number"] == "CUST-001"
+
+    def test_list_customers_pagination(
+        self, db, admin_customer_service, multiple_customers
+    ):
+        """Test pagination."""
+        # Get first page
+        customers, total = admin_customer_service.list_customers(db, skip=0, limit=2)
+        assert len(customers) == 2
+        assert total == 5
+
+        # Get second page
+        customers, total = admin_customer_service.list_customers(db, skip=2, limit=2)
+        assert len(customers) == 2
+
+        # Get last page
+        customers, total = admin_customer_service.list_customers(db, skip=4, limit=2)
+        assert len(customers) == 1
+
+
+@pytest.mark.unit
+class TestAdminCustomerServiceStats:
+    """Tests for get_customer_stats method."""
+
+    def test_get_customer_stats_empty(self, db, admin_customer_service, test_vendor):
+        """Test stats when no customers exist."""
+        stats = admin_customer_service.get_customer_stats(db)
+
+        assert stats["total"] == 0
+        assert stats["active"] == 0
+        assert stats["inactive"] == 0
+        assert stats["with_orders"] == 0
+        assert stats["total_spent"] == 0
+        assert stats["total_orders"] == 0
+        assert stats["avg_order_value"] == 0
+
+    def test_get_customer_stats_with_data(
+        self, db, admin_customer_service, multiple_customers
+    ):
+        """Test stats with customer data."""
+        stats = admin_customer_service.get_customer_stats(db)
+
+        assert stats["total"] == 5
+        assert stats["active"] == 3  # 0, 2, 4
+        assert stats["inactive"] == 2  # 1, 3
+        # with_orders = customers with total_orders > 0 (1, 2, 3, 4 = 4 customers)
+        assert stats["with_orders"] == 4
+        # total_spent = 0 + 100 + 200 + 300 + 400 = 1000
+        assert stats["total_spent"] == 1000.0
+        # total_orders = 0 + 1 + 2 + 3 + 4 = 10
+        assert stats["total_orders"] == 10
+
+    def test_get_customer_stats_by_vendor(
+        self, db, admin_customer_service, test_customer, test_vendor
+    ):
+        """Test stats filtered by vendor."""
+        stats = admin_customer_service.get_customer_stats(db, vendor_id=test_vendor.id)
+
+        assert stats["total"] == 1
+
+    def test_get_customer_stats_avg_order_value(
+        self, db, admin_customer_service, customer_with_orders
+    ):
+        """Test average order value calculation."""
+        stats = admin_customer_service.get_customer_stats(db)
+
+        # total_spent = 250, total_orders = 5
+        # avg = 250 / 5 = 50
+        assert stats["avg_order_value"] == 50.0
+
+
+@pytest.mark.unit
+class TestAdminCustomerServiceGetCustomer:
+    """Tests for get_customer method."""
+
+    def test_get_customer_success(self, db, admin_customer_service, test_customer):
+        """Test getting customer by ID."""
+        customer = admin_customer_service.get_customer(db, test_customer.id)
+
+        assert customer["id"] == test_customer.id
+        assert customer["email"] == test_customer.email
+        assert customer["first_name"] == test_customer.first_name
+        assert customer["last_name"] == test_customer.last_name
+
+    def test_get_customer_with_vendor_info(
+        self, db, admin_customer_service, test_customer, test_vendor
+    ):
+        """Test vendor info in customer detail."""
+        customer = admin_customer_service.get_customer(db, test_customer.id)
+
+        assert customer["vendor_name"] == test_vendor.name
+        assert customer["vendor_code"] == test_vendor.vendor_code
+
+    def test_get_customer_not_found(self, db, admin_customer_service):
+        """Test error when customer not found."""
+        with pytest.raises(CustomerNotFoundException):
+            admin_customer_service.get_customer(db, 99999)
+
+
+@pytest.mark.unit
+class TestAdminCustomerServiceToggleStatus:
+    """Tests for toggle_customer_status method."""
+
+    def test_toggle_status_activate(
+        self, db, admin_customer_service, test_customer, test_admin
+    ):
+        """Test activating an inactive customer."""
+        # Make customer inactive first
+        test_customer.is_active = False
+        db.commit()
+
+        result = admin_customer_service.toggle_customer_status(
+            db, test_customer.id, test_admin.email
+        )
+        db.commit()
+
+        assert result["id"] == test_customer.id
+        assert result["is_active"] is True
+        assert "activated" in result["message"]
+
+    def test_toggle_status_deactivate(
+        self, db, admin_customer_service, test_customer, test_admin
+    ):
+        """Test deactivating an active customer."""
+        test_customer.is_active = True
+        db.commit()
+
+        result = admin_customer_service.toggle_customer_status(
+            db, test_customer.id, test_admin.email
+        )
+        db.commit()
+
+        assert result["id"] == test_customer.id
+        assert result["is_active"] is False
+        assert "deactivated" in result["message"]
+
+    def test_toggle_status_not_found(
+        self, db, admin_customer_service, test_admin
+    ):
+        """Test error when customer not found."""
+        with pytest.raises(CustomerNotFoundException):
+            admin_customer_service.toggle_customer_status(
+                db, 99999, test_admin.email
+            )