Background: Recent progress in chemotherapy and targeting antibodies has brought an increased opportunity of conversion to curative resection in initially unresectable/metastatic colorectal cancer (CRC). Survival of CRC patients with liver metastasis who underwent conversion therapy was reported better than that of those who received palliative systemic therapy without surgery. However, it is largely unknown whether such patients who undergo conversion therapy can uniformly benefit from the surgical resections. Methods: We retrospectively reviewed 172 patients who received systemic therapy for unresectable CRC with synchronous liver metastasis in our hospital between 2010 and 2020. Patients were divided into ‘Conversion’ group (n = 45) and ‘Non-conversion’ group (n = 127) according to conversion to surgical resection with curative intent. Patients were also divided by pre-treatment Fong’s Clinical Risk Score (CRS), in addition to Grade A, B, or C group according to Japanese Grade Classification for colorectal liver metastasis. Overall survivals (OS) of Conversion and Palliation groups were compared according to these risk classifications. Results: Overall, 3-year OS rate was 76% for Conversion group and 25% for Non-conversion group (p < 0.001). Three-year OS rate for patients in Conversion group with CRS 1-3 was 73%, whereas that for those with CRS 4-5 was 77%. Both were higher than the rates for the counterparts in Non-conversion group (26% and 24%, respectively; both p < 0.001). When confined to Grade A and B of Japanese Grade Classification, 3-year OS rate was 68% for Conversion group and 25% for Non-conversion group (p = 0.002). The 3-year OS rate for the patient groups was 83% and 25% respectively in the analyses of patients classified into Grade C (p < 0.001). Conclusions: Conversion therapy provided a significant survival benefit in CRC patients with liver metastasis regardless of risk groups by the above classifications. Both classifications did not discriminate OS curves well between Conversion and Non-conversion groups in the era of conversion therapy.