Background <p>The clinical utility of staging laparoscopy (SL) after chemotherapy for advanced gastric cancer remains unclear. This study evaluated the diagnostic performance of post-chemotherapy SL and the prognostic significance of peritoneal disease resolution.</p> Methods <p>We retrospectively analyzed 128 patients who underwent SL after chemotherapy. Peritoneal disease was defined as macroscopic peritoneal dissemination and/or positive peritoneal lavage cytology. Diagnostic accuracy, sensitivity, and specificity of post-chemotherapy SL were evaluated. We examined the incidence of newly detected peritoneal disease among patients who were negative before chemotherapy and the rate of peritoneal/cytologic (P/CY) resolution among those who were positive before chemotherapy. Survival outcomes were compared according to post-chemotherapy P/CY status.</p> Results <p>The overall positivity rate of post-chemotherapy SL was 38.3%. Newly detected peritoneal disease on post-chemotherapy SL was observed in 2.8% of initially negative patients; when false-negative cases were considered, the actual rate was 5.6%. Among 92 patients with peritoneal disease before chemotherapy, the true P/CY resolution rate after excluding false-negative cases was 37.0%. Patients who achieved P/CY resolution had significantly better survival than those with persistent peritoneal disease (median survival time, 53.7 vs. 21.5&#xa0;months). Persistent P/CY positivity was an independent adverse prognostic factor.</p> Conclusions <p>Post-chemotherapy SL appears to be most useful as a patient selection tool, particularly in patients with peritoneal disease at initial diagnosis, by identifying those who may benefit from subsequent treatment escalation. In contrast, newly detected peritoneal disease was uncommon in initially negative patients. Careful interpretation is required because of the risks of false-negative findings and early peritoneal recurrence.</p>