An apparatus and method for reducing power consumption in a multi-mode portable terminal are provided. The apparatus includes a Subscriber Identity Module (SIM) management unit and a control unit. The SIM management unit is configured to determine whether there are multiple SIM cards of the same serving cell in a portable terminal supporting a plurality of RF modules and a plurality of SIM cards. The control unit is configured to activate only one RF module corresponding to the SIM cards of the same serving cell when receiving information of the SIM cards of the same serving cell from the SIM management unit.