Antibody-mediated rejection(AMR) in ABO incompatible(ABOi) kidney transplant(KT) patients can either be due to donor-specific anti-HLA antibody(DSA) or anti-blood group antibody. The relative frequency and possible phenotype difference of these two types of AMR in ABOi KT patients have not been reported.   Among 111 ABOi KT patients between 2007 and 2019 in our center, 15(13.5%) patients developed acute AMR diagnosed by indication biopsy. Since there is no histologic distinction between DSA- and anti-ABO-induced AMR, we assumed the causative antibody based on anti-ABO level and DSA at the time of AMR. Since low anti-ABO titer is unlikely to cause rejection and DSA can be undetectable in DSA-induced AMR by graft adsorption, AMR with lower anti-ABO titer and undetectable DSA is included in DSA-AMR group.   Of these 15 cases of AMR, 5 were attributable to anti-ABO (higher anti-ABO titer, undetectable DSA). 8 cases were attributable to DSA (5 with lower anti-ABO titer and detectable DSA, 3 with lower anti-ABO titer and undetectable DSA). 2 cases (higher anti-ABO titer, detectable DSA) were regarded as undetermined. The onset of AMR was within 2 weeks in all cases and comparable between two types of AMR. Initial anti-ABO titer was not statistically different; median(range) 256(64-4096) in ABO-AMR and 64(16-256) in DSA-AMR. All the 5 patients with ABO-AMR had negative PRA, whereas 4 of 8 patients with DSA-AMR had positive PRA before KT, and one DSA-AMR patient had persistent DSA before KT and at the time of AMR. All the AMR were recovered by treatment and no graft was lost to rejection. We conclude that a significant proportion of AMR in ABOi KT is caused by DSA, and clinical features and possible differential therapeutic approaches of these 2 types of AMR need to be explored by further studies.