About 20%-25% of patients experience weight regain (WR) or insufficient weight loss (IWL) following bariatric surgery (BS). Therefore, we aimed to retrospectively assess the effectiveness of adjunct treatment with semaglutide in patients without type 2 diabetes (T2D) with post-bariatric treatment failure over a 12 months period. Post-bariatric patients without T2D with WR or IWL (n = 29) were included in the analysis. The primary endpoint was weight loss 12 months after initiation of adjunct treatment. Secondary endpoints included change in body mass index, HbA1c, lipid profile, high sensitive C-reactive protein and liver enzymes. Total weight loss during semaglutide treatment added up to 14.7% ± 8.9% (mean ± SD, p < .001) after 12 months. Categorical weight loss was >5% in 89.7% of patients, >10% in 62.1% of patients, >15% in 34.5% of patients, >20% in 24.1% of patients and > 25% in 17.2% of patients. Adjunct treatment with semaglutide resulted in sustained weight loss regardless of sex, WR or IWL and type of surgery. Among patients with prediabetes (n = 6), 12 months treatment led to normoglycemia in all patients (p < .05). Treatment options to manage post-bariatric treatment failure are scarce. Our results imply a clear benefit of adjunct treatment with semaglutide in post-bariatric patients over a 12 months follow-up period.