OBJECTIVE—Our aim was to evaluate the long-term effects of transplanted islets on diabetic macro-/microangiopathy in type 1 diabetic kidney-transplanted patients. RESEARCH DESIGN AND METHODS—A total of 34 type 1 diabetic kidney-transplanted patients underwent islet transplantation and were divided into two groups: successful islet-kidney transplantation (SI-K; 21 patients, fasting C-peptide serum concentration >0.5 ng/ml for >1 year) and unsuccessful islet-kidney transplantation (UI-K; 13 patients, fasting C-peptide serum concentration <0.5 ng/ml). Patients cumulative survival, cardiovascular death rate, and atherosclerosis progression were compared in the two groups. Skin biopsies, endothelial dependent dilation (EDD), nitric oxide (NO) levels, and atherothrombotic risk factors [von Willebrand factor (vWF) and d-dimer fragment (DDF)] were studied cross-sectionally. RESULTS—The SI-K group showed a significant better patient survival rate (SI-K 100, 100, and 90% vs. UI-K 84, 74, and 51% at 1, 4, and 7 years, respectively, P = 0.04), lower cardiovascular death rate (SI-K 1/21 vs. UI-K 4/13, χ2 = 3.9, P = 0.04), and lower intima-media thickness progression than the UI-K group (SI-K group: Δ1–3 years −13 ± 30 μm vs. UI-K group: Δ1–3 years 245 ± 20 μm, P = 0.03) with decreased signs of endothelial injuring at skin biopsy. Furthermore, the SI-K group showed a higher EDD than the UI-K group (EDD: SI-K 7.8 ± 4.5% vs. UI-K 0.5 ± 2.7%, P = 0.02), higher basal NO (SI-K 42.9 ± 6.5 vs. UI-K 20.2 ± 6.8 μmol/l, P = 0.02), and lower levels of vWF (SI-K 138.6 ± 15.3 vs. UI-K 180.6 ± 7.0%, P = 0.02) and DDF (SI-K 0.61 ± 0.22 vs. UI-K 3.07 ± 0.68 μg/ml, P < 0.01). C-peptide-to-creatinine ratio correlated positively with EDD and NO and negatively with vWF and DDF. CONCLUSIONS—Successful islet transplantation improves survival, cardiovascular, and endothelial function in type 1 diabetic kidney-transplanted patients.