The association between widowhood and mental health problems, such as depressive symptomatology and anxiety, has been examined extensively. Few studies, however, have explored the prevalence and incidence of mood and anxiety disorders based on diagnostic criteria after the loss of the partner. We conducted a systematic review, and searched major bibliographical databases for studies examining mood and anxiety disorders in widowhood. We included all studies examining the prevalence or incidence of mood and anxiety disorders in the widowed, according to diagnostic criteria as assessed with a structured diagnostic interview. Eleven studies were identified, exploring the prevalence and incidence of mood and anxiety disorders in 3,481 widowed individuals and 4,685 non-widowed controls. As expected, the prevalence of Major Depressive Disorder (MDD) and anxiety disorders were considerably elevated in widowed individuals, especially in the first year after the loss of a spouse. During the first year of bereavement, almost 22% of the widowed were diagnosed as having MDD; almost 12% met diagnostic criteria for Post Traumatic Stress Disorder; and there were higher risks of Panic Disorder and Generalized Anxiety Disorder. The incidence rate of MDD and several anxiety disorders ranged from 0.08-0.50. The relative risk of developing a mood or anxiety disorder ranged from 3.49-9.76, in the widowed, compared to control subjects.