Vascular complications after a renal transplant are rare and critical. Duplex Doppler evaluation constitutes the primary imaging modality in renal transplant. Early diagnosis and appropriate intervention to address potential complications are crucial in graft survival. This report describes a 25-year-old woman who underwent a live-donor renal transplant. During a routine study 4 hours after surgery, she was found to have high peak flow velocities suggestive of stenosis. An angiogram obtained as a result of this finding showed no abnormalities. A repeat duplex Doppler sonogram performed 12 hours later revealed normal waveforms and velocities. Postrenal transplant vascular complications are rare but may represent a significant morbidity factor for patients and grafts. Peak wave forms, elevated velocities, and a tardus-parvus configuration are suggestive of vascular disorders that require aggressive evaluation. In our patient, the Doppler ultrasound, angiogram, and lack of clinical signs were compatible with a renal artery vasospasm. This entity, despite its reversibility in the majority of instances, may cause severe graft injury if it does not regress promptly.