People with bipolar disorders may have relapse of mood episodes associated with sleep deprivation and postpartum states. Jet lag can cause sleep problems resulting in relapse of mood episodes in vulnerable people. Melatonin synthesized in the pineal gland will normalize the circadian rhythm and prevent the recurrence of mood episodes in predisposed people. We are reporting a case of successful use of melatonin in a 30-year old lady with history of postpartum onset mood disorder and multiple relapses of mania precipitated by jet lag.