Antipsychotic induced weight gain is the most common and distressing side effect. This also affects the compliance toward the treatment and hence the prognosis. Non - pharmacological interventions such as exercise and diet modifications alone might not be sufficient most of the times; also ensuring compliance toward this is difficult in patients with psychiatric illness. So, the role of weight - reducing drugs become important. In this case report, we describe the use of low - dose topiramate as a weight - reducing agent, in a patient with a bipolar affective disorder - mania with psychotic symptoms, who had significant risperidone - induced weight gain.