Most studies investigating visuospatial decision-making emphasize interactions in fronto-parietal networks. These direct cortical connections are paralleled by indirect routes through the thalamic pulvinar, raising the question which information pulvinar contributes to visuospatial decision-making. Previous studies have shown that lesions or microstimulation of the dorsal pulvinar (dPul) induce an overt spatial selection bias, similar to spatial extinction observed following cortical lesions. Since our previous tasks always required a saccade towards one of the targets, and did not involve difficult perceptual discrimination, it remains unclear whether this bias is caused by perceptual or motor decision-related factors. Here we assessed changes in perceptual sensitivity and response criterion with reversible pharmacological inactivation of dPul. Two monkeys performed a color discrimination task where the perceptual difficulty was determined by the color similarity of target vs. distractor (red vs yellow, red vs orange). Target or distractor was either presented alone or with a second stimulus (distractor or target) in the opposite hemifield. Monkeys had to saccade to the target or to continue fixating when only distractor(s) were presented. The neurons in dPul were pharmacologically silenced by the GABA agonist, THIP. Data were analyzed using the signal detection framework. We expected a decrease in sensitivity if dPul affects perceptual discrimination and a shift in response criterion if dPul contributes to the motor decision signal. We primarily observed criterion shifts towards ipsilateral selection, especially when two competing peripheral stimuli were presented. Effects were similar across difficulty levels. In addition, the reaction time for contralateral stimuli was increased for all conditions. The perceptual sensitivity, and correspondingly, the overall success rate, remained largely unaffected. These results are consistent with the role of dPul in contraversive facilitation of visuospatial decision signals.