There is an increased interest among patients with bipolar disorder for using medical cannabis. The aim of this review was to elucidate, whether medical cannabis has a potential role in the treatment of bipolar disorder. Only one study with two case reports has been conducted. The two manic patients showed no improvement during the treatment but tolerated cannabis, and no side effects were reported. Overall, there is a lack of evidence for the use of cannabis in bipolar disorder. Future randomised clinical trials are warranted.