Purpose: This study was to determine the efficacy and safety of pemetrexed based chemotherapy in treating patients with metastatic gastric cancer who failed to respond to first and (or) second line chemotherapy. Patients and Methods: Metastatic gastric cancer patients who failed first and (or) second line chemotherapy, were enrolled. All patients were recruited from Jiangsu Cancer Hospital & Research Institute, and were treated with pemetrexed $500mg/m2$ (intravenous; on day 1), and a platinum (or irinotecan) every 3 weeks until disease progression, or intolerable toxicity. Evaluation on efficacy was conducted after two cycles of chemotherapy using the Response Evaluation Criteria for Solid Tumors. Toxicity was recorded according to National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Results: From Jun 2011 to May 2013, 23 patients were enrolled. All eligible 23 patients completed at least 2 cycles of chemotherapy with pemetrexed based chemotherapy, and were evaluable. Their median age was 55 years (range 40 to 78 years). Seventeen patients were male and 6 female. Three patients (13%) achieved partial response, five patients (22%) stable, 15 patients (65%) with disease progression, and none with complete response. Grade 2 neutrophil suppression occurred in 4.3%, grade 3 in 13% of patients, and no grade 4 was reported. Thrombocytopenia was encountered as follows: 4.3% grade 2, 4.3% grade 3 and 4.3% grade 4. Incidence of anemia was 34.8% in grade 2, 8.7% grade 3 and 0% grade 4. Only 4.3% of patients required packed red blood cell infusion. Elevated transaminase were 4.3% in grade 2 and 0% in grade 3 or 4. Other toxicity included oral mucositis. Conclusions: Pemetrexed based chemotherapy is mildly effective in treating patients with metastatic gastric cancer with tolerable toxicity.