AIM: To evaluate the antidepressant effect of aqueous extract of Aegle marmelos leaves in Swiss male albino mice by tail suspension method. MATERIALS AND METHOD: 30 inbred adult male albino mice (20 – 25 grams) will be procured from central animal house, Madurai Medical college, Madurai. Animals will be preconditioned in the lab for one week before the experiment to get accustomed to the lab condition. They will be divided into five groups of six animals in each group. Group I will served as control received normal feed and water, group II as standard received tablet Fluoxetine (20mg/kg ) orally, group III, IV,V as test groups received Aegle marmelos extract (75,150 & 300 mg/kg ) orally. The antidepressant effect of Aegle marmelos was evaluated using tail suspension test (TST) and the decrease in duration of immobility was compared with the standard drug Fluoxetine. RESULTS:The values obtained were expressed as mean ± SD. Statistical analysis of differences between groups was carried out using one–way analysis of variance (ANOVA). Probability (P) value of <0.05 was taken as the level of statistical significance. It is concluded that aqueous extract of Aegle marmelos possess potential antidepressant effect when comparable to that of tablet Fluoxetine.