A communication device for handling a cellular-wireless local area network, cellular-WLAN, aggregation, CWA, comprising: a storage device, for storing instructions of: receiving a first configuration configuring a CWA for a radio bearer, from a first cell of a cellular network; enabling the CWA for the radio bearer in response to the first configuration; communicating a plurality of cellular protocol data units, PDUs, associated to the radio bearer via a wireless local area network, WLAN, with the cellular network, when enabling the CWA for the radio bearer; receiving a handover command from the first cell, when enabling the CWA, wherein the handover command configures the communication device to perform a handover to a second cell of the cellular network; keeping enabling the CWA for the radio bearer in response to the handover command, when the handover command comprises a second configuration; and releasing the CWA for the radio bearer in response to the handover command, when the handover command does not comprise the second configuration; and a processing circuit, coupled to the storage device, configured to execute the instructions stored in the storage device; wherein the first configuration comprises a first CWA configuration information element, IE, configuring the CWA for the radio bearer, the first configuration does not comprise a specific IE, and the second configuration comprises the specific IE, and wherein the specific IE indicates to keep using the first configuration. a storage device, for storing instructions of: receiving a first configuration configuring a CWA for a radio bearer, from a first cell of a cellular network; enabling the CWA for the radio bearer in response to the first configuration; communicating a plurality of cellular protocol data units, PDUs, associated to the radio bearer via a wireless local area network, WLAN, with the cellular network, when enabling the CWA for the radio bearer; receiving a handover command from the first cell, when enabling the CWA, wherein the handover command configures the communication device to perform a handover to a second cell of the cellular network; keeping enabling the CWA for the radio bearer in response to the handover command, when the handover command comprises a second configuration; and releasing the CWA for the radio bearer in response to the handover command, when the handover command does not comprise the second configuration; and receiving a first configuration configuring a CWA for a radio bearer, from a first cell of a cellular network; enabling the CWA for the radio bearer in response to the first configuration; communicating a plurality of cellular protocol data units, PDUs, associated to the radio bearer via a wireless local area network, WLAN, with the cellular network, when enabling the CWA for the radio bearer; receiving a handover command from the first cell, when enabling the CWA, wherein the handover command configures the communication device to perform a handover to a second cell of the cellular network; keeping enabling the CWA for the radio bearer in response to the handover command, when the handover command comprises a second configuration; and releasing the CWA for the radio bearer in response to the handover command, when the handover command does not comprise the second configuration; and a processing circuit, coupled to the storage device, configured to execute the instructions stored in the storage device; wherein the first configuration comprises a first CWA configuration information element, IE, configuring the CWA for the radio bearer, the first configuration does not comprise a specific IE, and the second configuration comprises the specific IE, and wherein the specific IE indicates to keep using the first configuration.