It is one of the largest piranhas, reaching a maximum length of 50 cm in the wild, and is sometimes considered the most beautiful, with its orange to yellow belly coloration, silver eyes, and rayed fibrous adipose fin.

Like most other piranhas, P. piraya is laterally compressed and roughly circular in profile, and bears a mouthful of very sharp teeth.

Like most in the Serrasalmidae family, piraya piranhas dental morphology has a major influence for their inclination toward piscivorous and herbivorous behavior[3].

Members of this genus bear one row of sharp, triangular teeth with a strong lower jaw, which enable them to slice and mince prey with ease[4].

The piranha mostly prefers to eat small fish and insects, along with seeds and aquatic plant material.