Abstract Introduction To determine risk factors for and the effects of impaired perfusion (IP)—“reduced or non-perfusion”—of graft areas supplied by an accessory artery on allograft function. Objectives One hundred five consecutive grafts with multiple renal arteries were prospectively evaluated using Doppler ultrasound (US) to detect the perfusion of allograft segments supplied by the accessory artery. We studied factors predicting and the effects of IP on graft function. Results Doppler US diagnosed IP of allograft accessory arteries in 11 (10.5%) allografts. Mean values ± standard deviations and median (range) of renographic clearance of grafts with IP were 50.5 ± 26 and 40 (range, 21–92) mL/min, while those of grafts with patent accessory arteries were 68.6 ± 18.9 and 67.2 (range 21–117; P < .01). The percentage change in renographic clearance before versus after transplantation increased among grafts with patent arteries and decreased for those with IP (P = .03). On multivariate analysis, factors predicting IP of the accessory artery were delayed graft function (odds ratio [OR] = 9.9; 95% confidence interval [CI] = 1.6–58.6; P = .01) and upper polar arteries (OR = 8.9; 95% CI = 1.8–43.4; P < .01). Conclusion When considering transplants with accessory arteries, greatest attention and efforts should be exerted on upper polar arteries to avoid delayed graft function.