Acute interstitial nephritis (AIN) is an important cause of reversible acute kidney injury and pathologically characterized by inflammatory infiltrate in the renal interstitium. Solanum nigrum (S. nigrum) is a medicinal plant member of the Solanaceae family. Although S. nigrum has been traditionally used to treat various ailments such as pain, inflammation, and fever, it has also been reported to have a toxic effect, resulting in anticholinergic symptoms. However, there have been no reports of AIN caused by S. nigrum. Here, we report the first case of biopsy-confirmed AIN after ingestion of S. nigrum. The patient was successfully treated using corticosteroid therapy.