Neuropeptide S (NPS) is a recently discovered peptide shown to be involved in regulating arousal and anxiety. NPS receptor (NPSR) mRNA is expressed significantly in the major input and output regions of hippocampal formation, which are critical in the modulation of learning and memory. However, the role of NPS/NPSR system in regulating of learning and memory is still unknown. Here, we use the Morris water maze (MWM) to determine the effects of NPS on spatial learning and memory following intracerebroventricular (i.c.v.) injection in mice. Our data show that i.c.v. injection of NPS facilitates spatial memory in the MWM without significant alteration of latency to the target and swimming speed. Furthermore, NPS (i.c.v.) mitigates spatial memory impairment induced by the selective N-methyl-d-aspartate receptor antagonist MK801. Taken together, our results firstly demonstrate that NPS facilitates spatial memory and mitigates MK801-induced spatial memory impairment in mice.