Background: Neoadjuvant chemotherapy is promising to improve the survival of resectable gastric cancer. Cisplatin/S-1 (CS) and docetaxel/cisplatin/S-1 (DCS) are both active for metastatic gastric cancer. Methods: We conducted a randomized phase II trial to compare two and four courses of neoadjuvant S-1/cisplatin (SC) and docetaxel/cisplatin/S-1 (DCS) using a two-by-two factorial design for locally resectable advanced gastric cancer. Patients with M0 and either T4 or T3 in case of junctional cancer or schirrhous type received two or four courses of cisplatin (60 mg/m² at day 8)/S-1 (80 mg/m² for 21 days with 1 week rest) or docetaxel (40 mg/m² at day 1)/cisplatin (60 mg/m² at day 1)/S-1 (80 mg/m² for 14 days with 2 weeks rest) as neoadjuvant chemotherapy. Then, patients underwent D2 gastrectomy and adjuvant S-1 chemotherapy for 1 year. The primary endpoint was 3-year overall survival. The planned sample size was 120 eligible patients in total so that the treatment group with the superior observed 3-year OS rate by more than 60% as compared with 50% of the control group was to be selected with a probability of 85% or higher. Results: Between October 2011 and September 2014, 132 patients were assigned to CS (n = 66; 33 in 2-courses and 33 in 4-courses) and DCS (n = 66; 33 in 2-courses and 33 in 4-courses). The 3-year OS was 58.1% (95% CI, 45.8-70.3%) in CS and 60.0% (95% CI, 48.0-71.9%) in DCS with hazard ratio of 0796 (95% CI, 0.475-1.335), while that was 53.1% (95% CI, 40.9-65.4%) in the two courses and 65.0% (95% CI, 53.2-76.8%) in the four courses with hazard ratio of 0.722 (95% CI, 0.429-1.216). In the survival analysis by duration in each regimen, the 3-year OS was 58.1% (95% CI, 45.8-70.3%) both for two and four courses in CS, while that was 48.5% (95% CI, 31.4-65.5%) for two courses of DCS and was 71.9% (95% CI, 56.3-87.5%) for four courses of DCS. Conclusions: Considering high 3-year OS, four courses DCS has a value to be tested in a future phase III study to confirm superiority of neoadjuvant chemotherapy for locally advanced gastric cancer. Clinical trial information: UMIN000006378.