In this paper we present a novel particle swarm optimization (PSO) multiuser detection (MUD) approach for multiple-in-multiple-out (MIMO) systems with space-time block code (STBC). The proposed strategy consider the MUD problem with diversity reception from a multiobjective optimization (MO) viewpoint and develop a Pareto-optimal PSO-based (POPSO) algorithm. By taking advantage of the Pareto-optimal values, this approach effectively explores and exploits the channel fading information of received signals that are independent for each receive antenna, and accordingly improves the heuristic search ability to find the optimal solution. The proposed approach is shown to achieve superior bit-error-rate (BER) performance by simulations.