Objectives: In this study, the antileishmanial effect of different extracts of Euphorbia myrsinites aerial part was evaluated on promastigotes of Leishmania major in vitro.Materials and Methods: Dried and ground aerial parts of the plant were extracted using either maceration in 80% ethanol or soxhlet in methanol. Then 5 different concentrations of each extract, one positive control, one negative control, and one solvent control were prepared and placed in a 24-well plate containing 40,000 parasites/well. The extract concentrations were 0.06, 0.12, 0.25, 0.5 and 1 mg/ml. Amphotricin B (0.5 mg/ml) was used as positive control while negative control contained only culture medium. The plate was incubated at 25°C for six days, and the amount of parasites in each well was determined on days 2, 4, and 6 of experiment microscopically using Neubar chamber. Results: It was observed that amphotricin B and both macerated and soxhlet extracts at concentration of 1 mg/ml killed all parasites. Lower doses exhibited a dose-dependent antileishmanial activity. The ECso for macerated and soxhlet extracts in DMSO was between 0.5 and 0.25 mg/ml. The control solvents had no significant effect on the L. major promastigotes.Conclusion: These results indicated that both macerated and soxhlet extracts of E. myrsinites have favorable leishmanicidal activity.