Objective: To identify the rates and the predictors of long-term remission and the recurrence of type 2 diabetes mellitus (T2DM) after Roux-en-Y gastric bypass (RYGBP) or sleeve gastrectomy (SG). Background: The durability of the improvement of T2DM after bariatric surgery is not well characterized. Methods: One hundred fifty-three subjects with T2DM (RYGBP: n = 98; SG: n = 55) were evaluated for remission and recurrence of the disease throughout 35.4 ± 13.5 months' follow-up. The type of surgery, demographic, anthropometric, and biochemical parameters were ascertained as predictors of T2DM outcomes. Glucagon-like peptide 1 (GLP-1) responses after a standard mixed liquid meal were compared between patients presenting with T2DM remission after RYGBP or SG. Results: 75.2% of subjects presented with remission of T2DM lasting at least 12 months. However, in 12.1% of subjects, T2DM recurred. Regression analysis showed a longer duration of T2DM (P = 0.006), a higher presurgical glycated hemoglobin level (P = 0.019), insulin treatment at baseline (P = 0.001), and a lower excess weight loss at last follow-up visit (P < 0.001) as independent predictors for the lack of T2DM remission. Insulin use before surgery (P = 0.005), an older age (P = 0.05), and weight regain after remission (P = 0.021) predicted recurrence of the disease. Long-term remission of T2DM after SG or RYGBP was associated with a comparably enlarged GLP-1 response to a standard mixed liquid meal challenge. Conclusions: Roux-en-Y gastric bypass and SG are associated with comparable remission rates of T2DM. However, insufficient weight loss or weight regain in those with a more advanced disease may hamper the benefits of these surgical techniques on T2DM.