This phase II, open-label, single-arm study investigated sunitinib + FOLFIRI in Japanese patients with treatment-naïve unresectable/metastatic colorectal cancer. Patients received i.v. FOLFIRI (levo-leucovorin 200 mg/m2 + irinotecan 180 mg/m2, followed by 5-fluorouracil 400 mg/m2 bolus then 2400 mg/m2 46-h infusion) every 2 weeks, and oral sunitinib 37.5 mg/day on Schedule 4/2 (4 weeks on, 2 weeks off), until disease progression or treatment withdrawal. Progression-free survival (PFS) was the primary endpoint, with a target median of 10.8 months (35% improvement over FOLFIRI alone). Seventy-one patients started a median of 3 (range 1–11) sunitinib cycles (median relative dose intensity, <60%). The median PFS was 6.7 months (95% confidence interval, 4.7–9.2) by independent review, 7.2 months (95% confidence interval, 5.4–9.5) by investigator assessment. Objective response rate (complete responses + partial responses) was 36.6% (independent review) and 42.3% (investigator assessment). Clinical benefit rate (complete responses + partial responses + stable disease) was 83.1% (independent review) and 88.7% (investigator assessment). Common all-causality, any-grade, adverse events were: neutropenia and leukopenia (both 97.2%); thrombocytopenia (84.5%); diarrhea and nausea (both 78.9%); decreased appetite (74.6%); and fatigue (66.2%). Neutropenia (96%) was the most frequent grade 3/4 adverse event. This study was closed early due to findings from a concurrent phase III study of sunitinib + FOLFIRI in non-Japanese patients with metastatic colorectal cancer. In conclusion, the median PFS for sunitinib + FOLFIRI in Japanese patients was shorter than the 10.8 month target, indicating that sunitinib did not add to the antitumor activity of FOLFIRI. This study was registered with (NCT00668863). (Cancer Sci, doi: 10.1111/j.1349-7006.2012.02320.x, 2012)