Background: Optimal adjuvant chemotherapy after laparoscopic surgery in gastric cancer (GC) patients is still undefined. We aimed to evaluate the efficacy of S-1 plus oxaliplatin (SOX) and capecitabine plus oxaliplatin (CAPOX) in patients with GC after laparoscopic gastrectomy. Methods: A non-inferiority randomized controlled clinical trial was performed in China. Patients with advanced GC who underwent laparoscopic D2 gastrectomy were randomly assigned to receive SOX and CAPOX regimens. Results: In total, 191 patients were screened between May 2018 and June 2019, and 140 (73.3%) were included in the modified intent-to-treat analysis (mITT), of whom 69 and 71 were assigned to the SOX and CAPOX groups, respectively. The SOX group had similar 3-year overall survival (OS) and disease-free survival to the CAPOX group. Subgroup analysis revealed significantly better OS in the SOX group for male patients ([HR] = 0.395; 95% [CI], 0.153-1.019; p = 0.045), age >60 (HR = 0.219; 95% [CI], 0.064-0.753; p = 0.016), tumors in the gastric antrum (HR = 0.273; 95% [CI], 0.076-0.981; p = 0.047), and moderately differentiated tumors (HR = 0.338; 95% [CI], 0.110-1.041; p = 0.041). There were no significant differences observed in terms of adverse events and recurrence patterns between the two groups. Conclusion: Adjuvant SOX was non-inferior to CAPOX treatments for patients with GC who underwent curative laparoscopic D2 gastrectomy. For male patients, aged >60 years, tumors in the gastric antrum, and moderately differentiated tumors, adjuvant SOX may achieve an improvement compared with CAPOX.