Torsion of the extraperitoneally transplanted kidney is rare complication with no clinical data in the literature. The authors present the case of a 44-year-old man with end-stage renal disease who received a kidney transplant from his father. On postoperative day 4, serum urea and creatinine levels increased and urine output decreased. Renal ultrasonography revealed the renal hilum to be rotated to the lateral pelvic border, causing mild pelvocaliectasis, and Doppler ultrasonography, the patients showed a poststenotic flow pattern. After the patient underwent urgent reoperation, all laboratory values and ultrasonography findings returned to normal. To the authors' knowledge, this is the first published case report of torsion of the extraperitoneally transplanted kidney. When posttransplant deterioration in renal function occurs, renal torsion should be considered in the differential diagnosis.