Antipredatory defense of pronghorn (Antilocapra americana) neonates (≤1 month old) by adult females (>18 months old) is well documented throughout the geographic range of this species. However, reports of male pronghorn defending neonates against predators are limited to a single study in northwestern Wyoming where occurrences were documented of adult males assisting female pronghorn in defending neonates against coyotes (Canis latrans). To our knowledge, defense of neonatal pronghorn by yearling males (12–18 months old) has not been reported previously for this species. We report occurrences of antipredatory defense of neonatal pronghorn by yearling males in southwestern South Dakota.