Exacerbation of symptoms in mood disorders such as bipolar disorders, major depressive disorders and premenstrual dysphoric disorders could be influenced by the hormonal changes of the menstrual cycles in female patients. Menarche has been related to onset of mood symptoms, which at times have been described as menstrual psychoses and could represent an early presentation of Pediatric bipolar disorders. Pediatric bipolar disorders appear to be characterized by less clearly defined mood episodes, shorter duration of these episodes, and different hallmark symptoms than in adults. This report describes a pediatric patient who had no previous psychiatric symptoms and for whom menstrual psychosis was the presenting symptom of bipolar disorder not otherwise specified.