The present study was conducted to evaluate the in vivo efficacy of pumpkin seeds as an alternative natural anthelmintic for chickens. Ninety Philippine Jolo native chickens of mixed sexes, aged 4-5 months and weighing 1-2 kg, were randomly distributed into three treatment groups with 30 chickens per group. Control group A was fed basic mash feed, group B received feed mixed with ground pumpkin seeds (2 g/bird per day), and group C received mebendazole-medicated feed (30 mg/kg body weight). Fifteen randomly selected chickens from each group were euthanized and necropsied before treatment, and the remaining fifteen in each group were euthanized and necropsied at 3 days after the end of the treatment. Gastrointestinal worm and fecal egg counts were determined. Three genera of helminths were identified from necropsy: Ascaridia spp., Heterakis spp., and Raillietina spp. Results indicate that compared to mebendazole, pumpkin seed was moderately effective in reducing worm counts of Ascaridia spp. and Raillietina spp., marginally active in reducing worm counts of Heterakis spp., and moderately effective in reducing egg output of the worms. The results suggest that pumpkin seed has the potential to be used as an alternative anthelmintic for chickens.