Data on the effectiveness of sleeve gastrectomy in improving or resolving type 2 diabetes mellitus (T2DM) and the metabolic syndrome (MS) are scarce. A twelve-month prospective study on the changes in glucose homeostasis and the MS in 91 severely obese T2DM subjects undergoing laparoscopic SG (SG; n = 39) or laparoscopic Roux-en-Y gastric bypass (GBP; n = 52), matched for DM duration, type of DM treatment, and glycemic control was conducted. At 12 months after surgery, subjects undergoing SG and GBP lost a similar amount of weight (%EBL: SG: 63.00 +/- 2.89%, BPG: 66.06 +/- 2.34%; p = 0.413). On that evaluation, T2DM had resolved, respectively, in 33 out of 39 (84.6%) and 44 out of 52 (84.6%) subjects after SG and GBP (p = 0.618). The rate of resolution of the MS (SG: 62.2%, BPG: 67.3%; p = 0.392) was also comparable. A shorter DM duration (p < 0.05), a DM treatment not including pharmacological agents (p < 0.05), and a better glycemic control (p < 0.05), were significantly associated with T2DM resolution in both surgical groups. Weight loss was not associated with T2DM resolution after SG or GBP, but was associated with resolution of the MS following the two surgical procedures (p < 0.05). Our data show that at 12 months after surgery, SG is as effective as GBP in inducing remission of T2DM and the MS. Furthermore, our data suggest that SG and GBP represent a successful an integrated strategy for the management of the different cardiovascular risk components of the MS in subjects with T2DM.