The symbol error rate (SER) and bit error rate (BER) of the multiple-input-multiple-output (MIMO) system with decision-feedback detection (DFD) are analyzed over a Rayleigh fading channel. By using the concepts of “event” and “state” related to error propagation due to the decision-feedback process, we present general closed-form expressions for the SER and BER of each layer over quadrature-amplitude modulation (QAM) or phase-shift keying (PSK) for an arbitrary number of transmit and receive antennas. We also derive the asymptotic BER and SER performances of each layer. Numerical results show that our analysis matches very well with the Monte Carlo simulation. Our approach can be extended to the exact performance analysis of various wireless communication systems.