In this paper, we investigate the secrecy performance of multiuser dual-hop relay networks where a base station (BS) communicates with multiple legitimate users via the assistance of a trustful regenerative relay in the presence of multiple eavesdroppers. In particular, the maximal ratio transmission (MRT) scheme is exploited at the BS and a threshold-based multiuser scheduling scheme is employed over the legitimate users, while concerning the imperfect decoding at the regenerative relay. Furthermore, we consider the passive eavesdropper scenario and non-colluding eavesdropping mode. In order to quantify the secrecy performance of the considered system, the new exact closed-form expression for the secrecy outage probability is derived. In addition, conducive and simple high SNR approximation for the secrecy outage probability is also presented, which capacitates further insights into the impact of key system parameters on secrecy performance. Numerical results are provided to verify our theoretical analyses and illustrate the impact of key system parameters on the secrecy outage performance.