The family Pipidae includes five genera and two subfamilies, Pipinae and Dactylethrinae. Pipinae is restricted to Central and South America, occurring in the Amazon and Atlantic forest. We analyzed sexual dimorphism, female fertility, and diet of Pipa arrabali from their range's southernmost portion in Serra do Cachimbo, Pará, Brazil, and compared it to previous studies on populations near Manaus. We found no sexual dimorphism in shape, but females are significantly larger than males. Nineteen of 31 females had tadpoles embedded under the skin. Females harbored more and smaller tadpoles than previously reported for other populations. Diet of P. arrabali at the end of the dry season consisted mainly of dipteran pupae, contrasting to Manaus populations, where tadpoles were the main item, therefore underscoring the importance of prey availability on frog diet composition.