Background <p>Although robotic gastrectomy is increasingly being employed worldwide in patients with gastric cancer, the advantages of robotic gastrectomy (RG) over laparoscopic gastrectomy (LG) remain unclear across different age and BMI groups. This study aims to compare short-term outcomes of RG and LG across different age and BMI groups.</p> Methods <p>We analyzed Japanese administrative claims data for patients who underwent RG or LG for gastric cancer between February 2019 and June 2023. The study included 17,786 patients. Multivariable Cox proportional hazard regression models, incorporating interactions between the surgical approach and age, were used to assess postoperative complications, costs, and hospital stay. BMI analyses were conducted similarly.</p> Results <p>RG was associated with fewer postoperative complications (grade IIIa or higher, <i>p</i> &lt; 0.001) and shorter hospital stays (<i>p</i> &lt; 0.001) compared to LG in most age groups. Age significantly influenced the relationship between the surgical approach and costs (<i>p</i> = 0.004), with RG having lower costs in older patients, while younger patients incurred lower costs with LG. BMI also affected the association between the surgical approach and complications (<i>p</i> = 0.048); with patients having a BMI ≥ 20&#xa0;kg/m² experiencing fewer complications with RG than LG.</p> Conclusions <p>RG offers greater benefits for elderly and/or non-underweight patients compared to LG.</p>