Objective:To assess the ovicidal and larvicidal activities of aqueous and ethanolic extracts of pawpaw seeds Carica papaya (Caricaceae) on the eggs and first stage larvae (L1) of Heligmosomoides bakeri. Methods:Eggs of this parasite were obtained from experimentally infested mice (Mus musculus) and larvae were from eggs after incubation at 25℃for about 72 hours. The eggs and larvae were exposed to ten different concentrations (0.125, 0.25, 0.375, 0.5, 0.75, 1.0, 1.25, 1.75, 2.25 and 2.75 mg/mL) of both aqueous and ethanolic extracts respectively for 72 hours. Distilled water and 0.05%ethanol used as placebo and negative control, respectively. Results:Placebo and negative control group all showed average 92%embryonnation, 98%egg hatching and 2%larval mortality, and did not affect development and larval survival. The extracts inhibited embryonic development, egg hatching and larval survival. In general, the ovicidal and larvicidal activities increased with increasing concentration of different extracts. The aqueous extract was found to be more potent on eggs than on larvae. At 2.75 mg/mL, only 8%of eggs embryonnated and 50%hatched to L1 vs 57%embryonic development and 79%hatching occurred in the ethanolic extract. However, this later extract was more efficient in preventing larval development producing 96%mortality as against 68%with the aqueous extract. Conclusions:These results shows the ovicidal and larvicidal properties of aqueous and ethanolic pawpaw seeds extracts.