A method is provided for performing, by a user equipment (UE), a power headroom reporting (PHR) procedure in a wireless communication system. The UE determines whether at least one PHR has been triggered and not canceled, and whether an uplink (UL) resource can accommodate a PHR media access control (MAC) control element (CE) plus its subheader as a result of a logical channel prioritization (LCP). The UE transmits the PHR MAC CE, if it is determined that the at least one PHR has been triggered and not canceled, and that the UL resource can accommodate the PHR MAC CE plus its subheader.