ObjectiveTo compare the safety of the incision along the upper umbilical margin (referred to as the “upper incision”) versus the transverse umbilical incision (referred to as the “transverse incision”) for single-port bariatric surgery, and to assess their effects on postoperative scar appearance and patient’s psychological adaptation. MethodsThis study was designed as a multi-center retrospective analysis. The patients who underwent bariatric surgery via the upper incision and transverse incision at The third People’s Hospital of chengdu, Plastic Surgery Hospital of the Chinese Academy of Medical Sciences, and the First Affiliated Hospital of Jinan University from December 2024 to April 2025. The incidence of postoperative complications and the pionts of scar appearance (evaluated using the POSAS 3.0 scale) and psychological adaptation (measured with the BODY-Q scale) between the two incision methods were compared. Furthermore, multiple linear regression model was employed to evaluate the impact of different incision methods on points of scar appearance and psychological adaptation. ResultsA total of 194 patients who underwent single-port bariatric surgery were included, with 134 in the transverse incision group and 60 in the upper incision group. There was no statistically significant difference in the total incidence of incision complications between the transverse and upper incision groups [11.9% (16/134) vs. 18.3% (11/60), χ2=0.93, P=0.335]. The transverse incision group showed significantly better outcomes than the upper incision group in the overall points of BODY-Q scale [(39.86±1.02) vs. (37.63±4.70), t=-6.09, P<0.001] and POSAS scale [(17.60±2.35) vs. (21.25±6.00), t=5.24, P<0.001]. After adjusting for potential confounding factors such as diabetic status, education level, smoking status, alcohol use, keloid tendency, and use of scar improvement products in the multiple linear regression model, the advantage of the transverse incision remained significant [β(95% CI) = –1.81 (–2.84, –0.78), P<0.001]. Conclusions This study demonstrates that the transverse incision significantly improves the overall appearance of the postoperative scar and enhances patient’s psychological adaptation compared to the upper incision in single-port bariatric surgery. This advantage persists independently after adjusting for multiple confounding factors. Therefore, the transverse incision could be considered a more favorable approach in terms of cosmetic outcomes and patient’s psychological adaptation.