The aim of the present study was to investigate the relationship between 10 psychotropic agents and worsening BMI from overweight to obesity among inpatients with schizophrenia. A total of 138 patients with schizophrenia were recruited in this retrospective study. We included 23 patients with worsening BMI, from overweight (24≤BMI<27 kg/m²) to obesity (BMI≥27 kg/m²), as the case group and 115 patients without a worse BMI as the control group. Data were analyzed to assess the relationships between psychiatric drug use and BMI that worsened from overweight to obesity. Of the 138 patients, 60.9% were men. Their mean age was 47.2±9.7 years, mean age of onset of disease was 32.2±10.4 years, and the mean length of illness 15.0±6.5 years. Valproic acid was found to have a significant impact on the worsening of BMI from overweight to obesity (P<0.05). Age at onset of disease, length of illness, and duration of hospitalization were not associated significantly with worsening of BMI from overweight to obesity. These results call for caution in using valproic acid in schizophrenic inpatients with BMIs indicating overweight or obesity.