Characteristic alterations in the urinary microbiome, or urobiome, are associated with renal transplant pathology. To date, there has been no direct study of the urobiome during acute allograft rejection. The goal of this study was to determine if unique urobiome alterations are present during acute rejection in renal transplant recipients. We performed shotgun metagenomic sequencing of 32 mid-stream urine samples obtained from 15 transplant recipients pre-transplant, 1- and 3-months post-transplant, and at time of rejection discovered with for-cause biopsy. Within individuals, there was a 40-60 % difference in urobiome composition from pre-to-post-transplant in both rejectors and non-rejectors. The taxa Ureaplasma was enriched in rejectors compared to non-rejectors. However, a greater number of microbial genes were enriched in non-rejectors compared to rejectors, except for genes associated with tetracycline resistance, the lysophosphatidic acid synthesis pathway, and tryptophanyl-tRNA synthetase. Together, our findings suggest that the urobiome is significantly altered post-transplant with certain taxa and/or microbial genes potentially associated with acute allograft rejection/inflammation.