A method and apparatus for transmitting a power headroom report (PHR) in a wireless communication system is provided. A user equipment (UE) transmits a first PHR for a first carrier group, which is configured by a first eNodeB (eNB), to a second eNB; and transmits ing a second PHR for a second carrier group, which is configured by the second eNB, to the first eNB. The first PHR and the second PHR include a PHR for a physical uplink control channel (PUCCH) regardless of whether simultaneous transmission of the PUCCH and a physical uplink shared channel (PUSCH) is configured or not.