A memory system includes a memory device including a plurality of segments; a processor configured to generate a Read-Modify-Write (RMW) command on a target segment address corresponding to a target segment among the plurality of segments; a scheduler configured to receive the RMW command from the processor and schedule the RMW command; and a RMW unit configured to execute the RMW command on the memory device according to control of the scheduler, wherein the scheduler compares, when a plurality of RMW commands received from the processor are pending, target segment addresses of the plurality of RMW commands to re-order the plurality of RMW commands.