Aim:The goal of the present study is to investigate the effect of age, diabetes mellitus, and body mass index (BMI) on the outcomes of carpal tunnel syndrome (CTS) surgery in patients with moderate CTS according to neurophysiological classification.Material and Methods:Postsurgical outcomes were evaluated via a nerve conduction study (NCS) six to nine months after the surgery. Patients were divided into two groups according to neurophysiological classification based on the findings of postsurgical NCS: patients with mild CTS (partial recovery) or normal NCS (complete recovery) were classified as surgical success, and patients with moderate to more severe CTS were defined as surgical failure.Results:Forty-seven patients who underwent surgery for moderate CTS were included in the study. The mean age of the patients with surgical success (47.3 ± 10.9 years) was significantly lower than that of patients with surgical failure (54.3 ± 12.6 years; p = 0.048). The mean BMI of the patients with surgical success (31.3 ± 4.03 kg/m2) was significantly lower than that of patients with surgical failure (36.75 ± 5.5 kg/m2; p < 0.001). Multivariate logistic regression analysis demonstrated that higher BMI (p = 0.003) and older age (p = 0.031) were independent prognostic factors for surgical failure. In addition, there was a statistically significant and strong correlation between postoperative CTS severity and BMI (rho = 0.606, p < 0.001).Conclusion:Advanced age and high BMI negatively affect the success of surgical treatment in patients with CTS.