Background The intrarenal resistive index (RI) is a promising tool for predicting renal graft outcomes. Due to the complexity of graft function and the presence of diverse contributing factors, however, the available data are inconclusive. Purpose To examine the performance of the RI 1 week after transplant in predicting allograft function at week 12, with an emphasis on the type of intrarenal artery used in the examination. Material and Methods A total of 58 first-time living-donor kidney-allograft-transplantation patients aged less than 50 years underwent Doppler ultrasonography (US) of the intrarenal arteries 1 week after engraftment. The RI was calculated for both the segmental (RI-C) and interlobar-arcuate (RI-P) arteries. Serum creatinine level and the creatinine reduction ratio (CRR) were determined at weeks 1 and 12 post transplantation. Results While the RI did not correlate with serum creatinine level and CRR at week 1, significant correlations were present between the RI and serum creatinine level (r = 0.28, P = 0.03 for both RI-C and RI-P) and CRR (r = -0.25, P = 0.05 for both RI-C and RI-P) at week 12. The sensitivity, specificity, positive predictive value, and negative predictive value of using RI-C in predicting abnormal 12-week serum creatinine level were 51.2%, 52.9%, 72.4%, and 31.3%, respectively; and 53.7%, 47.1%, 70.9%, and 29.6% for RI-P, respectively ( P > 0.99 for all comparisons). Conclusion Early post-transplantation RI correlates significantly with both serum creatinine level and creatinine reduction ratio 12 weeks after engraftment with intermediate predictive accuracy.