Studies on the effects of third-line chemotherapy (CT) in advanced gastric cancer (GC) patients are still scarce. The aim of this study was to evaluate the efficacy and safety of the modified 5-fluorouracil, leucovorin, and irinotecan (mFOLFIRI) regimen as a third-line CT in metastatic GC patients, after failure of fluoropyrimidine, platinum, anthracycline, and taxane. After failure of first-and second-line therapies, 42 patients received third-line FOLFIRI (180 mg/m(2) irinotecan and 400 mg/m(2) leucovorin administered concomitantly as a 90-minute intravenous (IV) infusion on day 1, followed by a 400 mg/m(2) 5-fluorouracil IV bolus then 2600 mg/m(2) continuous infusion over 46 hours), between January 2009 and December 2015. FOLFIRI was administered for a median of 6 cycles (range 4-12 cycles). Eight patients achieved partial response, while 13 patients showed stable disease, resulting in the overall response rate (ORR) of 19% and disease control rate (DCR) of 50%. The most frequent grade 3-4 hematological and non-hematological toxicities were neutropenia (14.2%) and diarrhea (7.1%). The median progression-free survival (PFS) and overall survival (OS) from the start of third-line CT were 3.8 months (95% confidence interval [CI], 3.0-4.5) and 6.8 months (95% CI, 5.6-7.9), respectively. According to the multivariate analysis, two factors were independently predictive of the poor OS: > 2 regions of metastasis (relative risk [RR], 2.6; 95% CI, 1.3-5.4) and a high level of carcinoembryonic antigen [CEA] (RR, 3.4; 95% CI, 1.6-7.4). In conclusion, FOLFIRI was well tolerated as third-line CT and showed promising PFS and OS in advanced GC patients, after failure of fluoropyrimidine, platinum, anthracycline, and taxane.