There is evidence that adenosine acting at A_2A receptors (A_2AR) can influence striatal plasticity and cognitive functions. We examined spatial working memory in wild-type (WT) and A_2A receptor knock-out (KO) mice using two assessments: the eight arm radial maze and a repeated trial Morris water maze (MWM) paradigm. Compared to WT littermates, A_2AR KO mice displayed enhanced working memory as evidenced by a decrease in escape latency in trial 2 compared to trial 1 in the repeated trial MWM, and by a reduction in working memory errors in the radial arm maze. Both MWM and radial maze results indicated that this enhancement of working memory in A_2AR KO mice was selective for this specific short-term memory. The decrease in escape latency in MWM was detected with an inter-trial interval of 15 s but not with intervals of 10 or 60 min. In the radial maze, spatial reference memory and memory retention after prolonged training (15 days but not 6 days) were not affected by the A_2AR KO. These results demonstrate preferential improvement in spatial working memory by genetic inactivation of the A_2AR and support a modulatory role of the A_2AR in spatial working memory in mice.