Frugivores, animals that consume fruits and seeds, play an essential role in growing and maintaining plant communities by dispersing the seeds contained in a frugivore’s excrement. Many Amazon rainforest trees rely on seasonal flooding and frugivorous fishes like piranhas and pacus (Serrasalmidae) to disperse fruits and seeds across vast distances. We compared tooth puncture performance among three serrasalmid species with varying tooth morphologies: (1)Piaractus brachypomus, a large herbivorous pacu; (2) Pristobrycon maculipinnis, an odd frugivorous piranha; and (3) Megapiranha paranensis, an extinct serrasalmid considered to be the sister taxon to all extant piranhas. We compared the force and work it takes for 3D printed tooth models, obtained from microCT scans, to puncture different fruits. We predicted that the blunter pacu tooth would require the most force to puncture fruit, emphasizing how broader contact areas produce greater damage to fruit cells, as documented for bats and primates. Megapiranha teeth behaved more like pacu teeth for softer oranges; however, for stiffer apples, pacu and piranha teeth had similar puncture mechanics. Pacu and Megapiranha teeth produced higher forces and work when biting stiffer fruit, as predicted. However, tooth performance was similar among serrasalmids when indenting softer fruit. Across all performance measures, Megapiranha tooth performance did not resemble that of piranhas, which parallels ancestral state reconstruction findings that piranha ancestors were herbivorous. However, piranha teeth performed similarly to pacus during initial puncture and were similar overall when processing softer fruit, only differing once teeth were fully indented in stiffer fruit. Our findings demonstrate functional diversity within frugivorous fishes, and broadly suggest that serrasalmids have functionally versatile dentitions.