We present a rare case of Acute Interstitial Nephritis (AIN) that occurred following a re-trial of clozapine in a 56-year-old lady with schizoaffective disorder. On initial trial of clozapine, this patient felt generally unwell with respiratory symptoms. Her inflammatory markers were raised and her renal function showed a mild, transient deterioration which normalised on the day of cessation of clozapine. Two years later, clozapine was re-trialled due the refractory nature of her psychiatric symptoms. She subsequently developed renal failure and AIN was confirmed by renal biopsy. Renal function improved after cessation of clozapine; however, she never fully regained normal renal function.