Unity3d 5.3.0 introduced JsonUtility class which will help you with JSON serialization and deserialization. But this class has some limitation, and one of them: "You cannot serialize\deserialize System.Guid type" That's a pity, especially if you're using System.Guid in your DTO objects. But, there are solutions: You can change a data type, for example, use System.String or System.UInt32 instead of System.Guid. But if you have a lot of code which uses your DTO objects it might be painful to refac...