The optimal neoadjuvant and adjuvant treatment for gastric cancer remains controversial. We conducted a phase II study using preoperative chemotherapy with modified FOLFOX6 followed by surgical resection and postoperative chemoradiation in patients with gastric carcinoma. Preoperative chemotherapy (two or three cycles) consisted of a 2-h infusion of oxaliplatin (100 mg/m2) and folinic acid (100 mg/m2) followed by a 46-h continuous infusion of 5-fluorouracil (5-FU; 2,400 mg/m2). Surgical resection was planned 4 weeks after the last chemotherapy cycle. Patients underwent postsurgical chemoradiation, receiving a total dose of 45 Gy and 5-FU continuous infusion (350 mg/m2/day). The primary end points were feasibility, overall response rate, and R0 resectability rate after preoperative chemotherapy. The secondary end points were tolerability, treatment-associated complications, disease-free survival, and overall survival. Nineteen patients were enrolled in this study. After neoadjuvant treatment, four patients (21.1%) experienced progressive disease, six patients (31.6%) showed partial remission, and nine patients (47.3%) showed stable disease. In 15 patients (78.9%) R0 resectability could be achieved. Eleven of these patients (73.3%) were able to undergo postoperative chemoradiation. Notably, eight (72.7%) of these patients were disease free and alive at median follow-up of 60 months. Chemotherapy associated neutropenia, neutropenic fever, and anastomotic dehiscence were observed. The combination of preoperative chemotherapy and postoperative chemoradiation is feasible in a significant subset of gastric cancer patients.