In visceral leishmaniasis (VL), development of alternative safe therapeutic strategy is gaining paramount wherein natural components of plant origin have prominence. We explored Coccinia grandis (L.) Voigt, a medicinal plant known in traditional folk medicine, for its antileishmanial efficacy. SDS-PAGE analysis of the C. grandis leaf extract (Cg-Ex) showed few protein bands about 14-66 kDa among which three (64.8, 55.8 and 15.3 kDa) were identified as serine protease inhibitors by reverse zymography. Since the virulence of Leishmania is also attributed by serine proteases, objective of the present study was to evaluate in vitro antileishmanial activity of Cg-Ex, targeting Leishmania donovani serine protease(s). Inhibition study of Cg-Ex in gelatin-zymogram and spectrophotometric assay revealed its strong inhibitory activity against bovine trypsin rather than chymotrypsin, and also showed significant inhibition of L. donovani serine protease(s). Further, studies with Cg-Ex were extended to estimate its antileishmanial efficacy with half maximal inhibitory concentration (IC50) at 308.0 ± 2.42 μg/ml along with significant morphological alterations. The results have demonstrated the potential of the serine protease inhibitor rich fraction of the C. grandis leaf extract against visceral leishmaniasis.