The objective of this study was to determine the phytoconstituents present in successive extracts and the antidepressant activity of methanolic extract of the spadix of Colocasia affinis. The preliminary phytochemical investigation indicated the presence of fats and fixed oils, steroids and triterpenoids in petroleum ether extract, steroids and triterpenoids in chloroform extract, flavonoids and tannins in methanol extract and carbohydrates in the aqueous extract. An in vivo test for antidepressant activity was performed on the methanolic extract of the plant at two different doses using force swim test and tail suspension test on an experimental animal model (rat). Imipramine was used as a standard drug for the study. The methanolic extract at 200 and 400 mg/kg, produced significant reduction (p<0.001) in the immobility period when compared with that of control group animals in both the tests. Thus, the result indicates that the methanolic extract exhibited significantly good antidepressant activity. Further investigation may be needed to understand the actual mechanism of action.