An apparatus and method for efficiently transmitting/receiving a control channel in a mobile communication system simultaneously supporting a synchronous High-Rate Packet Data (HRPD) system and an Orthogonal Frequency Division Multiplexing (OFDM) system. Power of a control channel to be transmitted is measured. The measured power is compared with marginal maximum power set by a higher layer. According to the comparison result, information indicating whether a previous reverse packet has been successfully received and power control information for controlling power of a reverse link is inserted and transmitted in at least one of a Medium Access Control (MAC) channel and an OFDM symbol.