A communication device for handling a radio resource control, RRC, connection resume procedure, comprising: a storage unit, for storing instructions; and a processing circuit, coupled to the storage unit, wherein the storage unit stores, and the processing circuit is configured to execute, the instructions of: receiving, by a RRC layer of the communication device, a first RRC connection resume request from an evolved packet system, EPS, mobility management, EMM, layer of the communication device; performing, by the RRC layer of the communication device, an access barring check to detect whether an access to a serving cell of the communication device is barred or the access to a serving cell of the communication device is not barred; after detecting that the access to the serving cell of the communication device is barred, the RRC layer of the communication device is further configured for: not releasing a resume UE context and a resumeldentity; informing the EMM layer of the communication device that a RRC connection resume failure occurs, the access to the serving cell is barred, and the resume UE context and/or the resumeldentity is available; and entering, by the EMM layer of the communication device, an EMM-IDLE mode with suspend indication. a storage unit, for storing instructions; and a processing circuit, coupled to the storage unit, wherein the storage unit stores, and the processing circuit is configured to execute, the instructions of: receiving, by a RRC layer of the communication device, a first RRC connection resume request from an evolved packet system, EPS, mobility management, EMM, layer of the communication device; performing, by the RRC layer of the communication device, an access barring check to detect whether an access to a serving cell of the communication device is barred or the access to a serving cell of the communication device is not barred; after detecting that the access to the serving cell of the communication device is barred, the RRC layer of the communication device is further configured for: not releasing a resume UE context and a resumeldentity; informing the EMM layer of the communication device that a RRC connection resume failure occurs, the access to the serving cell is barred, and the resume UE context and/or the resumeldentity is available; and entering, by the EMM layer of the communication device, an EMM-IDLE mode with suspend indication. receiving, by a RRC layer of the communication device, a first RRC connection resume request from an evolved packet system, EPS, mobility management, EMM, layer of the communication device; performing, by the RRC layer of the communication device, an access barring check to detect whether an access to a serving cell of the communication device is barred or the access to a serving cell of the communication device is not barred; after detecting that the access to the serving cell of the communication device is barred, the RRC layer of the communication device is further configured for: not releasing a resume UE context and a resumeldentity; informing the EMM layer of the communication device that a RRC connection resume failure occurs, the access to the serving cell is barred, and the resume UE context and/or the resumeldentity is available; and entering, by the EMM layer of the communication device, an EMM-IDLE mode with suspend indication. not releasing a resume UE context and a resumeldentity; informing the EMM layer of the communication device that a RRC connection resume failure occurs, the access to the serving cell is barred, and the resume UE context and/or the resumeldentity is available; and entering, by the EMM layer of the communication device, an EMM-IDLE mode with suspend indication.