To describe the 10-year outcomes of islet transplantation within the Swiss-French GRAGIL Network, in patients with type 1 diabetes experiencing high glucose variability associated with severe hypoglycemia and/or with functional kidney graft. We conducted a retrospective analysis of all subjects transplanted in the GRAGIL-1c and GARGIL-2 islet transplantation trials and analyzed components of metabolic control, graft function and safety outcomes over the 10-year period of follow-up. Forty-four patients were included between September 2003 and April 2010. Thirty-one patients completed a ten-year follow-up. Ten years after islet transplantation, median HbA1c was 7.2% [6.2-8.0] (55 mmol/mol [44-64]) vs 8.0% [7.1-9.1] (64 mmol/mol [54-76]) before transplantation (p<0.001). 17/23 (73.9%) recipients were free of severe hypoglycemia, 1/21 patient (4.8%) was insulin-independent and median C-peptide was 0.6 ng/ml [0.2-1.2]. Insulin requirements (UI/kg/day) were 0.3 [0.1-0.5] vs 0.5 [0.4-0.6] before transplantation (p<0.001). Median [IQR] β-score was 1 [0-4] (p<0.05 when comparing with pre-transplantation values) and 51.9% recipients had a functional islet graft at 10 years. With a 10-year follow up in a multicentric network, islet transplantation provided sustained improvement of glycemic control and was efficient to prevent severe hypoglycemia in almost 75% of the recipients.