Tumor necrosis factor alpha (TNFα) plays an important role in the pathogenesis of diabetic retinopathy (DR). The objective of this study is to investigate the effect of TNFα blockade on complications of DR. Experimental models of diabetes were induced with streptozotocin (STZ) injection or insulin 2 gene point mutation (Akita) in mice. Intravitreal (IVT) and intraperitoneal (IP) injections were used to deliver anti-TNFα antibody and saline control. TUNEL and activated caspase-3 staining were used to examine apoptotic cell death. Transcardially-perfused FITC-ConA and fluorescence microscopy were used to monitor leukocyte adhesion. Trypsin digestion was used to prepare retinal vasculature and quantify acellular capillary. The leakage of 3 H-mannitol into the retina was used to quantify the breakdown of blood-retinal barrier (BRB). TNFα blockade significantly prevented diabetes-related retinal leukostasis. The numbers of caspase 3-positive and TUNEL-positive cells were significantly increased in diabetic retina, but reduced due to anti-TNFα treatment. The increased acellular capillary by diabetes was significantly prevented by anti-TNFα treatment. Diabetes-caused BRB breakdown was prevented by antibody treatment at 3 and 6 months. IVT and IP routes of antibody delivery had similar efficacy and dose response curve. Among the examined dose ranges (1-10 μg/eye for IVT injection and 2-25 mg/kg for IP injection), the antibody inhibited complications of DR in a dose-dependent manner. These results suggest that anti-TNFα therapy is a potential therapeutic treatment for DR.