diff --git a/services/merchant-service-net/src/MerchantService.API/Application/Behaviors/IRequirePermission.cs b/services/merchant-service-net/src/MerchantService.API/Application/Behaviors/IRequirePermission.cs
new file mode 100644
index 00000000..f0a09878
--- /dev/null
+++ b/services/merchant-service-net/src/MerchantService.API/Application/Behaviors/IRequirePermission.cs
@@ -0,0 +1,18 @@
+using MerchantService.Domain.AggregatesModel.MerchantStaffAggregate;
+
+namespace MerchantService.API.Application.Behaviors;
+
+/// <summary>
+/// EN: Marker interface for commands that require a specific StaffPermission.
+///     Commands implementing this will be checked by PermissionAuthorizationBehavior.
+/// VI: Marker interface cho commands yêu cầu StaffPermission cụ thể.
+///     Commands implement interface này sẽ được kiểm tra bởi PermissionAuthorizationBehavior.
+/// </summary>
+public interface IRequirePermission
+{
+    /// <summary>
+    /// EN: The permission required to execute this command.
+    /// VI: Permission cần thiết để thực thi command này.
+    /// </summary>
+    StaffPermissions RequiredPermission { get; }
+}
diff --git a/services/merchant-service-net/src/MerchantService.API/Application/Behaviors/PermissionAuthorizationBehavior.cs b/services/merchant-service-net/src/MerchantService.API/Application/Behaviors/PermissionAuthorizationBehavior.cs
new file mode 100644
index 00000000..ea911b87
--- /dev/null
+++ b/services/merchant-service-net/src/MerchantService.API/Application/Behaviors/PermissionAuthorizationBehavior.cs
@@ -0,0 +1,72 @@
+using MediatR;
+using MerchantService.Domain.AggregatesModel.MerchantStaffAggregate;
+
+namespace MerchantService.API.Application.Behaviors;
+
+/// <summary>
+/// EN: MediatR pipeline behavior that checks permission claims from JWT token.
+///     Only applies to commands implementing IRequirePermission.
+///     Reads "permission" claims from HttpContext.User and converts to StaffPermissions bitmask.
+/// VI: MediatR pipeline behavior kiểm tra permission claims từ JWT token.
+///     Chỉ áp dụng cho commands implement IRequirePermission.
+///     Đọc "permission" claims từ HttpContext.User và chuyển sang StaffPermissions bitmask.
+/// </summary>
+public class PermissionAuthorizationBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
+    where TRequest : IRequest<TResponse>
+{
+    private readonly IHttpContextAccessor _httpContextAccessor;
+    private readonly ILogger<PermissionAuthorizationBehavior<TRequest, TResponse>> _logger;
+
+    public PermissionAuthorizationBehavior(
+        IHttpContextAccessor httpContextAccessor,
+        ILogger<PermissionAuthorizationBehavior<TRequest, TResponse>> logger)
+    {
+        _httpContextAccessor = httpContextAccessor;
+        _logger = logger;
+    }
+
+    public async Task<TResponse> Handle(
+        TRequest request,
+        RequestHandlerDelegate<TResponse> next,
+        CancellationToken cancellationToken)
+    {
+        // EN: Skip if command doesn't require permission check
+        // VI: Bỏ qua nếu command không yêu cầu kiểm tra permission
+        if (request is not IRequirePermission permissionRequest)
+            return await next();
+
+        var required = permissionRequest.RequiredPermission;
+        if (required == StaffPermissions.None)
+            return await next();
+
+        var user = _httpContextAccessor.HttpContext?.User;
+        if (user?.Identity?.IsAuthenticated != true)
+        {
+            _logger.LogWarning("EN: Permission check failed — user not authenticated for {Command}",
+                typeof(TRequest).Name);
+            throw new UnauthorizedAccessException("User not authenticated / Người dùng chưa xác thực");
+        }
+
+        // EN: Extract permission claims from JWT and convert to bitmask
+        // VI: Trích xuất permission claims từ JWT và chuyển sang bitmask
+        var permClaims = user.Claims
+            .Where(c => c.Type == PermissionConstants.ClaimType)
+            .Select(c => c.Value)
+            .ToList();
+
+        var granted = PermissionConstants.FromClaims(permClaims);
+
+        // EN: Check if user has "All" permission or the specific required permission
+        // VI: Kiểm tra user có "All" permission hoặc permission cụ thể cần thiết
+        if (granted == StaffPermissions.All || (granted & required) == required)
+            return await next();
+
+        _logger.LogWarning(
+            "EN: Permission denied — {Command} requires {Required}, user has {Granted}. " +
+            "VI: Từ chối quyền — {Command} yêu cầu {Required}, user có {Granted}.",
+            typeof(TRequest).Name, required, granted);
+
+        throw new UnauthorizedAccessException(
+            $"Permission denied: requires {required} / Từ chối quyền: yêu cầu {required}");
+    }
+}
diff --git a/services/merchant-service-net/src/MerchantService.API/Application/Commands/Staff/StaffCommands.cs b/services/merchant-service-net/src/MerchantService.API/Application/Commands/Staff/StaffCommands.cs
index b8de8b08..b490c8e0 100644
--- a/services/merchant-service-net/src/MerchantService.API/Application/Commands/Staff/StaffCommands.cs
+++ b/services/merchant-service-net/src/MerchantService.API/Application/Commands/Staff/StaffCommands.cs
@@ -2,6 +2,7 @@
 // VI: Commands quản lý nhân viên.
 
 using MediatR;
+using MerchantService.API.Application.Behaviors;
 using MerchantService.Domain.AggregatesModel.MerchantAggregate;
 using MerchantService.Domain.AggregatesModel.MerchantStaffAggregate;
 using MerchantService.Domain.Exceptions;
@@ -11,11 +12,12 @@ namespace MerchantService.API.Application.Commands.Staff;
 #region Invite Staff Command
 
 /// <summary>
-/// EN: Command to invite a new staff member.
-/// VI: Command để mời nhân viên mới.
+/// EN: Command to invite a new staff member. Requires ManageStaff permission.
+/// VI: Command để mời nhân viên mới. Yêu cầu quyền ManageStaff.
 /// </summary>
-public record InviteStaffCommand : IRequest<InviteStaffResult>
+public record InviteStaffCommand : IRequest<InviteStaffResult>, IRequirePermission
 {
+    public StaffPermissions RequiredPermission => StaffPermissions.ManageStaff;
     /// <summary>
     /// EN: Owner's user ID extracted from JWT claims by the controller.
     /// VI: User ID của chủ merchant được lấy từ JWT claims bởi controller.
@@ -96,8 +98,9 @@ public class InviteStaffCommandHandler : IRequestHandler<InviteStaffCommand, Inv
 /// EN: Command to create a staff member directly as Active (when owner creates IAM account for them).
 /// VI: Command để tạo nhân viên trực tiếp Active (khi chủ DN tạo tài khoản IAM cho họ).
 /// </summary>
-public record CreateActiveStaffCommand : IRequest<InviteStaffResult>
+public record CreateActiveStaffCommand : IRequest<InviteStaffResult>, IRequirePermission
 {
+    public StaffPermissions RequiredPermission => StaffPermissions.ManageStaff;
     /// <summary>
     /// EN: Owner's user ID extracted from JWT claims by the controller.
     /// VI: User ID của chủ merchant được lấy từ JWT claims bởi controller.
@@ -190,8 +193,9 @@ public class CreateActiveStaffCommandHandler : IRequestHandler<CreateActiveStaff
 /// EN: Command to update a staff member.
 /// VI: Command để cập nhật nhân viên.
 /// </summary>
-public record UpdateStaffCommand : IRequest<bool>
+public record UpdateStaffCommand : IRequest<bool>, IRequirePermission
 {
+    public StaffPermissions RequiredPermission => StaffPermissions.ManageStaff;
     /// <summary>
     /// EN: Owner's user ID extracted from JWT claims by the controller.
     /// VI: User ID của chủ merchant được lấy từ JWT claims bởi controller.
diff --git a/services/merchant-service-net/src/MerchantService.API/Program.cs b/services/merchant-service-net/src/MerchantService.API/Program.cs
index 8e15e61a..0bcd0b59 100644
--- a/services/merchant-service-net/src/MerchantService.API/Program.cs
+++ b/services/merchant-service-net/src/MerchantService.API/Program.cs
@@ -32,12 +32,17 @@ try
         cfg.RegisterServicesFromAssemblyContaining<Program>();
         cfg.AddOpenBehavior(typeof(LoggingBehavior<,>));
         cfg.AddOpenBehavior(typeof(ValidatorBehavior<,>));
+        cfg.AddOpenBehavior(typeof(PermissionAuthorizationBehavior<,>));
         cfg.AddOpenBehavior(typeof(TransactionBehavior<,>));
     });
 
     // EN: Add FluentValidation / VI: Thêm FluentValidation
     builder.Services.AddValidatorsFromAssemblyContaining<Program>();
 
+    // EN: Required for PermissionAuthorizationBehavior to read JWT claims
+    // VI: Cần thiết cho PermissionAuthorizationBehavior đọc JWT claims
+    builder.Services.AddHttpContextAccessor();
+
     // EN: Add controllers / VI: Thêm controllers
     builder.Services.AddControllers();
 
diff --git a/services/merchant-service-net/src/MerchantService.Domain/AggregatesModel/MerchantStaffAggregate/PermissionConstants.cs b/services/merchant-service-net/src/MerchantService.Domain/AggregatesModel/MerchantStaffAggregate/PermissionConstants.cs
new file mode 100644
index 00000000..d9946e0a
--- /dev/null
+++ b/services/merchant-service-net/src/MerchantService.Domain/AggregatesModel/MerchantStaffAggregate/PermissionConstants.cs
@@ -0,0 +1,37 @@
+namespace MerchantService.Domain.AggregatesModel.MerchantStaffAggregate;
+
+/// <summary>
+/// EN: Maps permission claim strings (from IAM role_claims) to StaffPermissions bitmask.
+/// VI: Map chuỗi permission claim (từ IAM role_claims) sang StaffPermissions bitmask.
+/// </summary>
+public static class PermissionConstants
+{
+    public const string ClaimType = "permission";
+
+    private static readonly Dictionary<string, StaffPermissions> Map = new(StringComparer.OrdinalIgnoreCase)
+    {
+        ["ViewSales"] = StaffPermissions.ViewSales,
+        ["ProcessPayment"] = StaffPermissions.ProcessPayment,
+        ["RefundOrder"] = StaffPermissions.RefundOrder,
+        ["ManageInventory"] = StaffPermissions.ManageInventory,
+        ["ViewReports"] = StaffPermissions.ViewReports,
+        ["ManageStaff"] = StaffPermissions.ManageStaff,
+        ["ManageSettings"] = StaffPermissions.ManageSettings,
+        ["All"] = StaffPermissions.All,
+    };
+
+    /// <summary>
+    /// EN: Convert JWT permission claim values to StaffPermissions bitmask.
+    /// VI: Chuyển đổi giá trị permission claim từ JWT sang StaffPermissions bitmask.
+    /// </summary>
+    public static StaffPermissions FromClaims(IEnumerable<string> claimValues)
+    {
+        var result = StaffPermissions.None;
+        foreach (var val in claimValues)
+        {
+            if (Map.TryGetValue(val, out var perm))
+                result |= perm;
+        }
+        return result;
+    }
+}