An apparatus for estimating a DOA in a MIMO system includes a receiver and a signal processor. The receiver receives Rx signals from a target through Rx antennas after Tx signals having different phases are transmitted through Tx antennas, and transforms the Rx signals into time domain Rx signals. The processor transforms the time domain Rx signals into Rx signals in a frequency domain including a range-related domain and a velocity-related doppler domain; divides the doppler domain into regions according to a phase difference between the Tx signals; extracts signals from the regions; combines the signals to form first and second arrays; determines a minimum value for each of the first and second arrays using a DML algorithm; selects one of the first and second arrays having the minimum value as a true array; and estimates a DOA corresponding to the true array as an actual DOA of the target.