The reproductive biology of Tantilla melanocephala was studied in eastern Amazonia, Pará, Brazil. Males and females attained sexual maturity at approximately twice the length (snout–vent length  =  SVL) of newborn snakes. Mature males had a larger tail length and more subcaudal scales than mature females, whereas females were larger (SVL) and had more ventral scales than males. Total length did not differ between mature males and females. Reproduction was not seasonal. There was no correlation between the number of vitellogenic follicles and oviductal eggs. The number of eggs was positively correlated with the female SVL. The data presented here indicate that the eastern Amazonia population differs from populations in southeastern Brazil in important morphological and reproductive aspects, including the mean number of eggs produced (mean  =  1.53), which was smaller in eastern Amazonian populations.