The significance of primary tumor resection for unresectable Stage Ⅳcolorectal cancer is controversial. In the present study, we examined cases of unresectable Stage Ⅳ colorectal cancer treated in our department. The subjects were 78 patients with unresectable Stage Ⅳ colorectal cancer who received either resection of the primary tumor, intensive chemotherapy, or both, between 2006 and 2012. The patients were divided into 2 groups: the group that received primary tumor resection (67 patients) and the non-resection group (11 patients). No differences were noted between a history of primary tumor resection and various clinicopathological factors, but the prognoses in the primary tumor resection group were favorable. The subjects were divided into 3 groups based on the selection of primary tumor resection and chemotherapy. The median survival time was 21.6 months, 11.8 months, and 8.1 months for patients who underwent chemotherapy after primary tumor resection (52 patients), patients who received primary tumor resection only (15 patients), and patients who received only chemotherapy (11 patients), respectively. The prognoses of patients who received primary tumor resection were favorable in comparison with those who received only chemotherapy. The results of the present study suggest the possibility that primary tumor resection can improve the prognoses of patients who have unresectable Stage Ⅳ colorectal cancer.