OBJECTIVE: To study the influence of methanolic and aqueous extract of Withania somnifera (W. somnifera) root on the marble-burying behavior of mice a well-accepted model of obsessive compulsive behavior. METHODS: Mice were divided in different groups (n = 6). Fluoxetine (5, 10, 15 mg/kg), (10, 25, 50, 100 mg/kg) and methanolic extract W. somnifera (MEWS) (10, 25, 50, 100 mg/kg) were administered i.p. 30 min. prior to the assessment of marble burying behavior and locomotor activity. The control group received vehicle of the extract. RESULTS: Administration of aqueous extracts W. somnifera (AEWS) and MEWS (50 mg/kg) successively decreased the marble burying behavior activity without affecting motor activity. This effect of AEWS and MEWS was comparable to standard fluoxetine, ritanserin and parachlorophenylalanine. CONCLUSIONS: W. somnifera extract is effective in treating obsessive compulsive disorder.