OBJECTIVE: To determine the association of antibodies against angiotensin II type 1 receptor (AT1R Ab) and histopathologic changes seen in patients with kidney allograft rejection and negative donor specific HLA antibodies (DSA). METHODS: Stored sera from 27 patients who had biopsy-proven rejection in the absence of DSA were tested for AT1R Ab. Biopsy slides of all patients were re-examined and classified according to Banff 2013 criteria. Histopathologic changes were compared between AT1R positive and negative patients. RESULTS: 75% of patients with positive pre-transplant AT1R Ab had antibody mediated rejection (AMR) compared to 37% of AT1R Ab-negative patients. A trend towards increased interstitial inflammation was observed in the AT1R Ab positive group (p=0.08). More patients in the AT1R Ab positive group had microcirculation inflammation (88% vs 58% with glomerulitis scores ≥1; 75% vs 58% with peritubular capillaritis scores ≥1). CONCLUSION: In kidney transplant recipients with rejection and no DSA, a higher incidence of AMR and worse inflammation scores are observed in the presence of positive pre-transplant AT1R antibodies.