Background: Obstructive nephropathy is an uncommon side effect of sulfadiazine, which is used for the treatment of toxoplasmosis. We present a case of acute renal colic and urine extravasation of a patient shortly after she was started on this medication. Case Presentation: A 31-year-old female presented with acute renal colic 2 weeks after starting treatment with sulfadiazine and pyrimethamine for ocular toxoplasmosis. Results: A noncontrast computed tomography revealed left hydronephrosis and fluid located around the kidney and in the left gutter. There were no urinary stones. Administration of intravenous contrast revealed significant urine extravasation at the level of the ureteropelvic junction. Intravenous contrast injection confirmed that the extravasation consisted of urine leakage at the ureteropelvic junction. Her clinical condition improved with the insertion of an internal stent, which was left in place for 4 weeks. A retrograde pyelography performed at the time of the internal stent removal ruled out persistent extravasation and filling defects in the left upper urinary tract. Considering the clinical circumstances and the imaging results, it appears that this is a first reported case of sulfadiazine-induced obstructive uropathy associated with urine extravasation. Conclusion: Although rare, obstructive uropathy related to sulfadiazine medication should be promptly suspected, diagnosed, and treated. Patients should be instructed to substantially increase their liquid intake while on that medication.