The multiple target localization using only Doppler frequencies in Multiple-Input Multiple-Output (MIMO) radar is a problem of great interest. The Doppler frequencies include all relevant information about the location, velocity and direction of the targets. Hence, these frequencies can be used efficiently for data association and target localization. The MIMO configuration and the frequency diversity of the system enable us to easily determine the number of moving targets using only the Doppler frequencies. Then, the data association is achieved for the known number of targets by using the estimated target velocities, directions and positions which can be utilized together or separately for data association. Using these parameters, three data association methods are proposed, namely "Position & Velocity Based", "Direction Based" and "Position, Velocity & Direction Based" Data Associations. Moreover, when probability of detection is less than unity, data association can still be achieved with some modifications. Besides that, another algorithm, referred to as "Frequency Reduction & Association", is proposed to eliminate spurious frequencies when they appear in the spectrum. These are the first data association methods for Doppler-only systems and they can be used efficiently when Doppler frequencies are only available information in the MIMO radar context. After received frequencies are associated with the correct targets, multiple target localization can be performed using the associated Doppler frequencies. (C) 2013 Elsevier Inc. All rights reserved.