Because standard chemotherapy for advanced gastric cancer consists of oral fluoropyrimidines plus platinum as first-line therapy, with paclitaxel plus ramucirumab as the second line, irinotecan is usually positioned as third-line chemotherapy in clinical practice in Japan.A retrospective evaluation was conducted to determine the efficacy and safety of irinotecan as third-line chemotherapy for advanced gastric cancer in patients refractory or intolerant to fluoropyrimidines, platinum, and taxanes.Between February 2008 and December 2013, 52 patients received third-line irinotecan monotherapy. Among the 32 patients with measurable lesions, 1 patient achieved a confirmed partial response and 6 patients had stable disease. The overall response rate was 3% and the disease control rate was 22%. Median progression-free survival was 2.3 months [95% confidence interval (CI), 1.8-2.8] and median overall survival was 4.0 months (95% CI, 2.6-5.3). The most common adverse events of grade 3 severity or higher were neutropenia (27%), febrile neutropenia (12%), anorexia (12%), and diarrhea (6%). Although no treatment-related deaths occurred, 2 patients (4%) died of disease progression within 30 days after the last administration of irinotecan.Irinotecan monotherapy appears to be tolerated but was shown to have modest activity as third-line chemotherapy for advanced gastric cancer.