A communication device for handling a radio resource control (RRC) reestablishment comprises at least one storage device and at least one processing circuit coupled to the at least one storage device. The at least one storage device stores instructions, and the at least one processing circuit is configured to execute the instructions of: detecting a failure; transmitting a first RRC Reestablishment Request message to a first radio access network (RAN) in response to the failure; receiving a first RRC Setup message for responding to the first RRC Reestablishment Request message, from the first RAN; and transmitting a first RRC Setup Complete message for responding to the first RRC Setup message, to the first RAN, wherein the first RRC Setup Complete message comprises a Fifth Generation (5G) System Architecture Evolution (SAE) Temporary Mobile Station Identifier (TMSI) (5G-S-TMSI).