A transmit power capability and power headroom report (PHR) method and an apparatus of a User Equipment (UE) operating in an Inter-evolved Node B (Inter-eNB) carrier aggregation or dual connectivity mode for use in a mobile communication system are provided. The transmit power capability and PHR method includes receiving configuration information for at least one medium access control (MAC) entity for transmitting and receiving a signal; receiving uplink resource allocation information for a first MAC entity included in the at least one MAC entity; and transmitting, if change of measurement on one of the at least one MAC entity is equal to or greater than a threshold, a power headroom report (PHR) on an uplink resource corresponding to the first MAC entity based on the uplink resource allocation information.