Hyperprolactinaemia may affect sexual and reproductive functioning. However, recent studies suggest that increased prolactin levels may also have negative effects on cognition. We aimed to study whether the reduction in prolactin levels by cabergoline in patients with hyperprolactinaemia is followed by an improvement in cognitive tasks. We studied seven patients with hyperprolactinaemia caused by a prolactinoma that had an indication to start treatment with cabergoline. All patients were assessed twice (baseline and 6–12 months after cabergoline treatment) with a cognitive battery. Plasma prolactin levels were determined. We found a significant improvement in the speed of processing, working memory, visual learning and reasoning and problem-solving domains after cabergoline treatment. Improvements in speed of processing and reasoning and problem solving were greater in patients with baseline prolactin levels above the median. In summary, a reduction in prolactin levels by cabergoline in patients with hyperprolactinaemia is followed by an improvement in cognitive abilities. This finding suggests that prolactin may be involved in cognitive processes, although cabergoline could also have procognitive effects that are independent of prolactin changes. Further clinical trials are needed to confirm the potential cognitive-enhancement properties of cabergoline in patients with chronic hyperprolactinaemia.