Hypoxia following arteriovenous fistulization results in venous neointimal hyperplasia (VNH), potentially causing early arteriovenous fistula (AVF) dysfunction. In this study, we used hyperbaric oxygen (HBO) in a rabbit model of AVF to determine whether it could ameliorate early AVF failure. Chronic renal failure was induced by adenine in 96 adult rabbits randomly divided into 3 groups (n=32 in each group). The sham + HBO group underwent sham operation and received HBO. The AVF alone group underwent fistulization, but did not receive HBO. The AVF + HBO group underwent fistulization and received HBO. Each group was further divided into 4 subgroups of 8 rabbits each that were euthanized at 1, 7, 14 or 28 days post-operatively. At each time point, blood flow changes in the AVF venous segment were detected using a high-frequency duplex ultrasonography system. Immunohistochemical staining for proliferating cell nuclear antigen (PCNA), and hematoxylin and eosin staining were performed to evaluate VNH. Western blot analysis was performed to confirm the expression of hypoxia-inducible factor (HIF)-1α. At 14 and 28 days following HBO treatment, blood flow in the AVF + HBO group was greater than that at day 0. The AVF + HBO group had a smaller ratio of intima to media area, a lower HIF-1α protein expression, and a smaller percentage of PCNA-positive cells in the proximal vein than did the AVF alone group. Our results thus suggest that continuous HBO treatment following AVF significantly inhibits VNH and promotes blood flow. Therefore, early AVF failure may be prevented by the use of HBO therapy.