The FOLFIRINOX combination of chemotherapy drugs had not been fully evaluated for Japanese pancreatic cancer patients. Therefore, we carried out a phase II study to examine the efficacy and safety of FOLFIRINOX in chemotherapy-naïve Japanese patients with metastatic pancreatic cancer. FOLFIRINOX (i.v. infusion of 85 mg/m2 oxaliplatin, 180 mg/m2 irinotecan, and 200 mg/m2 l-leucovorin, followed by a bolus of 400 mg/m2 fluorouracil and a 46-h continuous infusion of 2400 mg/m2 fluorouracil) was given every 2 weeks. The primary endpoint was the response rate. The 36 enrolled patients received a median of eight (range, 1–25) treatment cycles. The response rate was 38.9% (95% confidence interval [CI], 23.1–56.5); median overall survival, 10.7 months (95% CI, 6.9–13.2); and median progression-free survival, 5.6 months (95% CI, 3.0–7.8). Major grade 3 or 4 toxicities included neutropenia (77.8%), febrile neutropenia (22.2%), thrombocytopenia (11.1%), anemia (11.1%), anorexia (11.1%), diarrhea (8.3%), nausea (8.3%), elevated alanine aminotransferase levels (8.3%), and peripheral sensory neuropathy (5.6%). Febrile neutropenia occurred only during the first cycle. There were no treatment-related deaths. FOLFIRINOX can be a standard regimen showing favorable efficacy and acceptable toxicity profile in chemotherapy-naïve Japanese patients with metastatic pancreatic cancer.