Space-time transmission techniques, which make full use of the rich scattering channel with multiple transmit and receive antennas, can greatly increase the spectral efficiency. In this paper, parallel multistage decision feedback equalizer (DFE), which is composed of parallel interference cancellation, multiple input single output decision feedback equalizer (MISO-DFE) and linear combination of the soft outputs of MISO-DFE and the previous soft decisions, is proposed for a single-carrier system over layered space-time frequency-selective channels. In addition, an algorithm is proposed to obtain the soft and hard decisions for initialization. And the proposed parallel multistage DFE can be implemented with lower complexity than MIMO-OFDM. Simulation results show that the parallel multistage DFE outperforms the MIMO-OFDM and various previous equalizers for a single-carrier system.