A bi-directional resistive memory device includes a memory cell array including a plurality of memory cells and an input/output (I/O) circuit. The I/O circuit is configured to generate a first voltage having a positive polarity and a second voltage having a negative polarity, provide one of the first voltage and the second voltage to the memory cell array through a bitline responsive to a logic state of input data, and adjust magnitudes of the first and second voltage when data written in the memory cell array has an offset. Related memory systems and methods are also provided.