Objectives The aim of this study is to explore the family history of psychiatric disorders, childhood abuse, and stressors in older patients with Bipolar Disorder (BD) and the association of these variables with the age at onset of BD. Methods The Questionnaire for Bipolar Disorder (QBP) and the Mini International Neuropsychiatric Interview (MINI-Plus) were obtained from 78 patients aged 60 and over to determine diagnosis, age at onset of the first affective episode, childhood abuse, family history of psychiatric disorders and past and recent stressful life events. Results Increased family history of psychiatric disorders was the only factor associated with an earlier age at onset of BD. Less family history of psychiatric disorders and more negative stressors were significantly associated with a later age at onset of the first (hypo)manic episode. Limitations Age at onset, history of childhood abuse, and past stressful life events were assessed retrospectively. Family members of BD patients were not interviewed. Conclusions Our findings suggest that age at onset can define distinct BD phenotypes. More specifically there was a stronger heredity of BD and other psychiatric disorders in patients with an early age of onset of BD. Negative stressors may play a specific role in patients with a late age at onset of a first (hypo)manic episode.