Gastrointestinal nematodes are accounted for major economic losses in ruminant worldwide; however, several drug resistance has been reported. In the search for natural anthelmintic,Murraya paniculata  a medicinal plant indigenous to Thailand, was selected due to the reported anthelmintic properties of its leaf. The present study aimed to evaluate in vitro antiparasitic activity of M. paniculata aqueous extract. The in vitro killing assay was studied by incubated the Mecistocerus. digitatus with levamisole at a concentration 0.25, 0.5, 1, and 2 mg/ml or the aqueous extract of M. paniculata at 1, 10, 20, and 40 mg/ml. During 0-24 hours. The worms in all groups were gradually decreased in motility, where the dead worms could be observed only at 24 hours. The lethal dose at 50% (LD50) of levamisole and M. paniculata aqueous extract-treated group was at 0.32 and 32.99 mg/ml, respectively. The worms that were exposed to the extract at 40 mg/ml at 12 and 24 hours showed the alteration on the cuticle with swollen, bleb, and erosion. The result of this study showed that there were active anthelminthic substances in M. paniculata leaves aqueous extract. Further study is in need to purify the active constituents from M. paniculata leaves and test the effectiveness against M. digitatus both in vitro and in vivo.