A method and an apparatus for scheduling uplink transmissions according to a maximum transmission power and Power Headrooms (PHs) reported by a User Equipment (UE) are provided. A method for reporting the PHs for carriers used by a terminal in a mobile communication system supporting carrier aggregation includes generating a message including the PHs along with indicators indicating whether a real transmission is scheduled on an uplink data channel of corresponding carrier, and including, when the real transmission is scheduled, a maximum transmission power used for calculating the PHs in the generated message.