<b>Ovicidal and Larvicidal Effects of Crude Ethanolic Extracts of Acanthus Montanus Acanthaceae on Heligmosomoides Bakeri Nematoda, Heligmosomatidae </b> Objective An in vitro study was carried out to determine the ovicidal and larvicidal activity of crude ethanolic extracts of Acanthus montanus Acanthaceae leaves on the eggs and the third larval L3 stage of Heligmosomoides bakeri. Methods Four different concentrations of the extracts by serial dilution from 1,000 mg mL to 125 mg mL were compared with albendazole as the positive control serially diluted from the recommended dose of 15 mg mL to 1.875mg mL and distilled water serving as the negative control respectively, in the bioassay. The extract activity was dose dependent. Results At 250 mg mL, there was 100 inhibition of egg hatch comparable to albendazole at 7.5 mg mL. There was zero percent inhibition of eggs in the distilled water control culture. The activity of the extracts on the L3 larvae shows that at the concentration of 125 mg mL, the larvicidal effect was 100 , one hour post treatment compared to albendazole at 15 mg mL 97.51 . However, the negative control showed an increase in Larvicidal activity from 22.5 to 40 in one hour and fifteen hours respectively. Conclusion It was therefore, concluded that crude ethanolic extracts of Acanthus montanus leaf has significant ovicidal and larvicidal properties against Heligmosomoides bakeri egg and third larval stage. Acanthus montanus extract Heligmosomoides bakeri larvicidal, ovicidal 1646-1649 Issue-4 Volume-5 D. O. Oshadu | J. O. Ajanusi | P. N. Chiezey | M. S. Abubakar | M. Adamu | A. W. Adanu | G.A.I. Dogo