Beta-lactam-associated acute tubulointerstitial nephritis (ATIN) is a rare condition in childhood. We report the case of an infant with penicillin-associated ATIN and concomitant acute pyelonephritis resulting in the development of severe acute kidney injury (AKI). The treatment consisted of penicillin suspension and appropriate AKI management, which required a short period of dialysis. Finally, full recovery and normalization of laboratory parameters occurred. We present here the first case of oral penicillin-associated ATIN in childhood.