An apparatus and method for controlling a data rate by a user equipment (UE) that receives a scheduling command for uplink data transmission from a non-serving Node B in a mobile communication system that transmits packet data over an uplink are provided. A scheduling command receiver receives a down command for decreasing an allowable data rate of the UE from radio link sets (RLSs) of the non-serving Node Bs. A down command reception counter counts the number of down commands received from each of the RLSs for a predetermined hysteresis period. A down command execution counter counts the number of down commands executed for the hysteresis period. A down command execution decision unit compares the number of received down commands with the number of executed down commands, and determines whether to execute the down command according to the comparison result.