This narrative review addresses the challenges of how to identify and treat bipolar depression. Bipolar depression, i.e. depressive episode(s) as part of bipolar disorder, can be differentiated from unipolar depression only through the previous course of illness. A correct diagnosis therefore may be delayed. The pharmacotherapy of bipolar depression differs from that of unipolar depression due to a high risk of recurrence of either hypomanic/manic or depressive episodes or mood instability. Therefore, long periods of specialized treatment will often be required. Both bipolar and unipolar depression will often benefit from adjunctive social and psychological interventions.