The diagnosis of bipolar affective disorder in people with intellectual disability (ID) can be challenging due to the difficulties arising from communication problems, the influence of poor physical and social circumstances and a general lack of suitable diagnostic criteria. Mania and hypomania in ID present with an increase in motor activity. Rapid cycling bipolar disorder is associated with severe behaviour problems in individuals with ID, particularly self‐injurious behavior. Mixed episodes of symptoms of mania and depression are not uncommon in people with ID. Lithium has been successfully used in the prophylaxis of bipolar disorder in ID. Long‐term medication treatment should normally continue for at least 2 years after an episode of bipolar disorder. Electroconvulsive therapy (ECT) is recommended only to achieve rapid and short‐term improvement of severe symptoms after an adequate trial of other treatment options has proven ineffective and/or when the condition is considered to be potentially life threatening.