In this paper, it is proposed that a particle swarm optimization (PSO) based partial transmit sequence (PTS) technique is used so that least Peak-to-Average Power Ratio(PAPR) is achieved in Multiple Input Multiple Output- Orthogonal Frequency Division Multiplexin gsystems (MIMO-OFDM). Our approach is to apply PSO based PTS on each antenna of the system helping to find the optimal phase factors, which is a straightforward method to achieve minimum PAPR in this system. PSO based PTS algorithm when applied to MIMO-OFDM systems with a wide range of phase factors, results in high performance after simulation. The results PAPR achieved for 16X16 MIMO-OFDM systems without PTS using 16-QAM is 15.8dB whereas with PTS the PAPR achieved is 7.1 dB therefore overall reductions PAPR with and without PTS is 8.7 dB. Similarly PAPR achieved for 16X16 MIMO-OFDM systems without PTS-PSO using 16-QAM is 15.8 dB whereas with PTS-PSO the PAPR achieved is 3.6 dB therefore overall reductions PAPR with and without PTS is 12.2 dB. The final reduction in PAPR resulted as 8.7 dB and 12.2 dB respectively.