BACKGROUND: People with schizophrenia or bipolar disorder (BD) exhibit very high levels of obesity. Little is known about the potential benefits/risks of obesity surgery. We conducted a narrative review to summarize the available knowledge on bariatric surgery in people with schizophrenia or BD. METHODS: A systematic search was conducted of major electronic databases from inception to October 2016 for studies investigating bariatric surgery among people with schizophrenia or BD. Data were presented in a narrative synthesis and future research strategies proposed. RESULTS: The electronic database searches identified 44 records. Eight studies (BD, n = 265; schizophrenia: n = 14) were included with a mean study length of 15.7 months (12-24). Seven found that bariatric surgery resulted in weight loss in those with psychiatric disorders with an excess weight loss ranging -31 to -70%. Six studies found that weight loss from bariatric surgery was similar in people with schizophrenia or BD versus controls. However, most of the studies limited their outcomes to only weight loss and did not measure whether obesity surgery affected the status and treatment of psychiatric symptoms. Although few adverse events were reported among patients with BD, data from two studies demonstrated no significant deterioration of psychiatric symptoms post-surgery in people with schizophrenia. CONCLUSIONS: Growing evidence suggests that bariatric surgery may improve short-term weight status among people with BD. However, given the paucity of studies for schizophrenia, and the lack of information on medium-to long-term results, future large-scale high-quality studies are required.