The objective of this study is to evaluate the veno-arterial index (VAI) as a predictor of renal rejection in kidney transplant patients. A diagnostic test study was conducted between January 2014 and May 2018. Renal transplant patients who underwent percutaneous renal biopsy were included. The VAI was obtained by measuring the flow velocity in the renal segmental vein and dividing this value by the peak systolic velocity of the segmental artery in this same location. The records of 77 patients were analyzed. Among these patients, 32 (42%) were positive for transplant rejection and 29 presented with acute rejection. In patients with renal rejection, the median VAI was 0.67 (interquartile range [IQR] = 0.56-0.87), and in kidneys with a negative biopsy for rejection, the median VAI was 0.41 (IQR = 0.27-0.57), with a statistically significant difference (P =.007) and a value much higher than that obtained for the general population of 0.30 (IQR = 0.18-0.44). Subacute and acute rejected kidneys had an even higher VAI of 0.725 (IQR = 0.57-0.87; P =.0001). Although the resistive index has a good correlation with glomerular filtration, it is not possible by that index to differentiate among the multiple causes that can lead to graft dysfunction. The results of this study show that the VAI might be a useful parameter, which when elevated could predict renal transplant rejection.