In the present study, in vitro anti- leishmanial activity of Ethyl acetate, Methanolic, Benzene and Chloroform extracts of Nyctanthes arbortristis have been evaluated. Among those extracts Methanolic extracts of Nyctanthes arbortristis shows effective antileishmanial activity against promastigote form of Leishmania donovani. Nycanthic acid,3-4,secotriterpene acid present in Nyctanthes arbortristis may be responsible for inhibiting the growth of parasite. It was found that LC50=150 pg/ml i.e. 50% inhibition at 100 pg/ml and LC90=200 pg/ml for complete inhibition is required to inhibit the growth of Leishmania donovani. The details have been discussed in the paper.