Whether primary tumor resection (PTR) should be performed in patients with asymptomatic colorectal cancer (CRC) and unresectable synchronous metastasis is controversial. The purpose of this study was to investigate the prognostic impact of initial primary tumor resection in patients with synchronous unresectable metastatic CRC. The patients with unresectable synchronous metastatic CRC who had undergone primary tumor resection and then received chemotherapy were compared with the patients who received only palliative systemic chemotherapy. Survival analysis showed that median overall survival (OS) for all patients was 22.37 months. Primary tumor resection was associated with a significant survival benefit on unadjusted analysis (median survival 29.56 months vs. 14.25 months; p<0.001). Two-year, 3-year and 5-year survival rates were 57%, 35%, 19% for the PTR group and 30%, 16%, 8% for the non-PTR group and all results were statistically significant and favored surgery. Our study suggests that primary tumor resection improves the survival of patients with metastatic CRC and unresectable synchronous metastasis.