A transdermal patch formulation of a non-steroidal anti-inflammatory drug (NSAID) used by a 44-year-old man resulted in acute interstitial nephritis and acute tubular injury. This patient also had a history of mild kidney dysfunction and osteoporosis. The NSAID patch had been prescribed after a traffic accident. He was also receiving a vitamin D analog and taking over-the-counter calcium supplements. Two months later, renal dysfunction and hypercalcemia were discovered. A renal biopsy showed acute interstitial nephritis and acute tubular injury. Once these agents were withdrawn, the renal function recovered. This is the first reported occurrence of biopsy-proven acute interstitial nephritis attributable to NSAID patch usage.