We report a case of a 22-month-old boy who suffered a piranha bite, amputating his fourth distal phalanx. His finger was irrigated and closed with a flap under sedation, but we could find little evidence during a brief literature search of what prophylactic antibiotics, if any, to provide. Because reports of infections from piranha bites are lacking, we examined studies evaluating oral flora from fish, as well as flora cultured from aquariums. In conclusion, if infection is present or prophylaxis is strongly desired, a broad spectrum oral antibiotic that covers Gram-positive and Gram-negative bacteria including Pseudomonas and Aeromonas species, such as ciprofloxacin, would be recommended; however, there is little evidence to suggest that prophylactic antibiotics provide benefit over appropriate wound management.