Exclusion of the proximal gut from nutrient absorption entails significant metabolic benefits. The duodenal-jejunal bypass liner (DJBL) is the first endoscopic device that excludes the first part of the gut by covering it. To assess weight and glycemic control at the end of treatment and after 1 year of follow-up. Bariatric endoscopy service in a tertiary medical center. Diabetic patients were treated with DJBL and followed prospectively between 2013 and 2016. Data were collected during scheduled visits. Out of 51 patients treated, 39 completed at least 9 months with the device. Complications were recorded for the entire cohort. Percent of total weight loss was 15.05% ± 6.0% after 12 months of treatment (P < .001 versus baseline). Twelve months postretrieval, percent of total weight loss decreased to 8.75% ± 5.07% (P < .001 versus baseline). Patients with baseline body mass index ≥35 kg/m experienced greater percent total weight loss changes over time (P < .001). There was a significant effect on hemoglobin A1C levels over time (P = .003), and the nadir was reached at 9 months of treatment (median 6.05% versus 7.20% at baseline, P < .001). Insulin users had consistently higher median hemoglobin A1C values compared with insulin nonusers (P < .001). Adverse events were experienced by 12 of 51 patients (23.5%), of which 4 cases (7.8%) were severe. Proximal bowel bypass by DJBL is an effective tool for weight reduction and glycemic control. Metabolic achievements are partially preserved at 1 year after device removal. Because DJBL entails a considerable rate of side effects, strategies to mitigate them are warranted.