Adiponectin has an important role in obesity, insulin resistance, and cardiovascular disease. We investigated the association between serum adiponectin levels and endothelial function in kidney transplant patients.Fasting blood samples were obtained from 70 kidney transplant patients. The vascular reactivity index was measured with a digital thermal monitoring test. Serum adiponectin levels were measured with a commercially available enzyme immunoassay kit. A vascular reactivity index <1.0 was defined as poor, 1.0 or greater but less than 2.0 was intermediate, and 2.0 or greater was good.The results showed that 10 kidney transplant patients (13.3%) were categorized with a vascular reactivity index of poor, 25 (35.7%) were intermediate, and 35 (50%) were good. Increased waist circumference (P = .037), increased serum alkaline phosphatase (P = .026), and lower serum adiponectin (P = .001) were associated with poor vascular reactivity index. Advanced age (r = -0.300; P = .012), waist circumference (r = -0.372; P = .002), serum alkaline phosphatase (r = -0.323; P = .006), and logarithmically transformed serum triglycerides (r = -0.317; P = .007) were negatively correlated with the vascular reactivity index, whereas serum adiponectin (r = 0.332; P = .005) was positively correlated with the vascular reactivity index. Multi variable forward stepwise linear regression analysis showed that waist circumference, serum alkaline phosphatase, and serum adiponectin were significantly and independently associated with the vascular reactivity index.Fasting serum adiponectin levels were positively associated with the vascular reactivity index and negatively associated with endothelial function in kidney transplant patients.