Orthogonal frequency division multiplexing (OFDM) is a strong candidate for 4G wireless networks, due to its high data rate and ability to combat frequency selective fading. OFDM may be combined with multiple-input multiple-output (MIMO) to increase the diversity gain and system capacity over the time-variant frequency-selective channels. However, a major drawback of MIMO-OFDM system is that the transmitted signals on different antennas might exhibit high peak-to-average power ratio (PAPR). The high PAPR leads to nonlinear distortion of the high-power-amplifier (HPA) and results in inter-carrier-interference (ICI) plus out-of-band radiation. In this paper, we present a Zadoff-Chu matrix transform (ZCMT) based space-time-block-coded (STBC) MIMO-OFDM system with reduced PAPR. Extensive simulations have been performed to analyze the PAPR of the proposed system with root-raised-cosine (RRC) pulse shaping. Simulation results show that, ZCMT precoded STBC MIMO-OFDM system has low PAPR when compared to both the Walsh-Hadamard transform (WHT) precoded STBC MIMO-OFDM systems and the conventional STBC MIMO-OFDM systems. © 2011 IEEE.