Background: Studies show that attempts to treat liver metastases during or before primary colonic cancer resection may improve survival. We aimed to compare overall survival of patients with colon cancer and liver metastases who underwent primary tumor resection with/without resection of liver metastases. Methods: This retrospective cohort study included patients with stage IV colon adenocarcinoma and isolated liver metastases who underwent surgical resection, using data from the National Cancer Database between 2015-2019. Patients with metastases to other organs or who did not have primary tumor resection were excluded. The cohort was divided into Colectomy-only (resection of primary colonic cancer only) and Colectomy-plus (resection of primary tumor and liver metastases) groups. After comparing, significant baseline and treatment confounders were identified and groups were matched using the nearest neighbor, 1:1 propensity-score method. Primary outcome was overall survival; secondary endpoints were short-term mortality and 30-day unplanned readmission. Results: 6780 patients who underwent primary tumor only resection and 4082 who underwent primary tumor and liver metastases resection were included. Patients in the Colectomy-only group were significantly older (63.73±13.59 vs 59.56±13.32 years;p < 0.001), more often male (56% vs 53.5%;p = 0.01), had more comorbidities (Charlson score 3: 4.4% vs 3.3%;p = 0.001) and right-sided colonic cancer (45.7% vs 43.2%;p = 0.002), shorter time before surgery (10 vs 30 days;p < 0.001), and more laparoscopic surgery (40.4% vs 35%;p < 0.001). Colectomy-only group patients had less chemotherapy (48.6% vs 50.7%, p = 0.04) and immunotherapy (34.1% vs 40.6%, p < 0.001) whereas Colectomy-plus group patients had more neoadjuvant systemic therapy (18.8% vs 10.2%;p < 0.001). Median overall survival of the Colectomy-plus group was significantly longer than Colectomy-only group (45.1 vs 24.4 months; p < 0.001). After matching for significant confounders, 2038 patients were included in each group. There were no significant differences between the two groups in 30-day (3.8% vs 3.1%;p = 0.3) and 90-day mortality (7.7% vs 6.6%;p = 0.2). Colectomy-plus group patients had significantly higher 30-day unplanned readmissions (7.2% vs 5.3%, p = 0.02) and significantly longer median overall survival (41.5 vs 28.4 months, p < 0.001). On Cox-regression analysis, resection of liver metastases and primary colonic tumor was associated with 33% mortality reduction (HR: 0.678, 95%CI: 0.618-0.745, p < 0.001). Conclusions: Resection of colonic cancer liver metastasis with the primary tumor is associated with significant survival benefit and may prolong survival by approximately 12 months, versus primary tumor resection alone. Synchronous resection of the primary tumor and liver metastases should be considered as it appears to offer survival benefit.