To address the problem of time and frequency offset estimation for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, a joint time and frequency synchronization algorithm based on constant amplitude zero auto correlation (CAZAC) sequences is proposed. The synchronization preamble consists of two training symbols with the same length. At the receivers, cross correlations between two local sequences and the received signal are calculated respectively, utilizing the unique properties of CAZAC sequences to detect the time offsets and integer frequency offsets of all the transmitter and receiver pairs. After compensating for the integer frequency offsets, fractional frequency offsets are obtained using the relationship between the two training symbols. Analysis and simulation results demonstrate that the proposed method not only has a significantly higher synchronization probability than conventional algorithm but also can estimate the frequency offsets of all the transmitter and receiver pairs.