BACKGROUND: Risky surgical manipulations that can cause postoperative intra-abdominal infections (IAICs) have not been identified in gastric cancer surgery. We conducted a study to evaluate surgical videos and identify risky surgical maneuvers. METHODS: This was a multicenter case-control study. Patients who underwent laparoscopic gastrectomy with lymph node dissection for gastric adenocarcinoma were enrolled in this study. Patients who developed IAICs after surgery were defined as cases, and a control group adjusted for patient background characteristics was selected using propensity score matching. Using an 11-item rating scale specific to gastric cancer surgery developed by experts, two raters blinded to the outcome scored the unedited surgical videos on a five-point scale. The mean difference in the scores for each item was evaluated to identify risky manipulations. We also evaluated the Objective Structured Assessment of Technical Skills (OSATS) as a general evaluation instrument. RESULTS: After excluding patients for whom a video evaluation was not possible, 121 cases and 114 controls were included in this analysis. Risky surgical maneuvers strongly associated with the occurrence of IAICs were identified, including accidental pancreatic injury during peri-pancreatic lymph node dissection, bleeding from the pancreas, improper hemostatic manipulation, and blunt compression of the pancreas. The reconstructive manipulations were not at risk, and all OSATS items were also significantly better in the control group than in the case group. CONCLUSION: We identified the risk of surgical manipulation associated with postoperative complications in this case-control study, with strict adjustment for patient risk factors.