Background: The standard treatment for synchronous stage IV colorectal cancer (CRC) is systemic chemotherapy. There have been attempts to conduct elective primary tumor resection (PTR) as an upfront treatment to prevent complications in primary tumor sites, or improve prognosis. However, there are controversies about the role of PTR in stage IV CRC. We investigated the prognostic role of PTR and tried to find subgroups who might get benefit from upfront PTR in this population. Methods: Between 2010 and 2020, 330 patients diagnosed with synchronous stage IV CRC at St. Vincent Hospital in Korea were retrospectively reviewed. We excluded patients underwent PTR and metastasectomy at the same time, PTR for emergencies (perforation, acute bleeding with hemodynamic instability, fistula, and/or obstruction), or received chemoradiotherapy as an initial treatment. Overall survival (OS) was measured from the date of diagnosis until death resulting from any cause or the last censored date during follow-up. OS were calculated using the Kaplan-Meier method, and differences in survival between groups were compared by the log-rank test. Variables with p value <0.05 were included in the Cox regression multivariable model. Results: Total 223 patients were analyzed. Patients were divided into two groups; 45 patients receiving upfront elective PTR (PTR group), and the 178 patients receiving upfront systemic treatment (non-PTR group). Two groups were not different in terms of age (p = 0.979), ECOG performance status (p = 0.488), and serum CEA levels (p = 0.252). However, the PTR group showed lesser number of metastatic organ compared to the non-PTR groups (p = 0007). The PTR group survived longer than the non-PTR group (p = 0.015). Multivariate analysis revealed that age≥60 (hazard ratio [HR], 1.55; 95% confidence interval [CI], 1.15-2.09; p = 0.004,), CEA≥30 ng/mL (HR, 1.32; 95% CI, 0.99-1.75, p = 0.061), PTR (HR, 0.66; 95% CI, 0.45-0.95; p =0.027), adding targeted agent (HR, 0.71; 95% CI, 0.53-0.96; p = 0.026), and ECOG≥3 (HR, 1.649; 95% CI, 1.15-2.37, p = 0.007) were associated with OS. Subgroup analysis showed that PTR might be beneficial in patients with low CEA (<30 ng/mL, p = 0.032), old age (≥60, p = 0.028), ECOG (≤2, p = 0.006), M1a stage (p = 0.008), and receiving bevacizumab (p = 0.016). Conclusions: Upfront PTR was conducted in selected patients with lower number of metastasis, but associated with OS after adjusting other prognostic factors. We suggested that PTR could be an option for patients with low CEA (<30 ng/mL), old age (≥60), ECOG (≤2), M1a stage, or receiving bevacizumab in this population.