Background and Objectives: In metastatic colorectal cancer, v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) is a predictive biomarker for anti-epidermal growth factor receptor (EGFR) treatment and V-raf murine sarcoma viral oncogene homolog B1 (BRAF) is a prognostic biomarker. We aimed to determine the impact of KRAS and BRAF mutation as determined from liver metastases specimens on overall survival (OS) in patients following colorectal liver metastasectomy. Methods: Liver metastases specimens (n = 292) obtained from patients after liver metastasectomy were used to determine the KRAS/BRAF genotype. Associations between clinicopathological parameters and KRAS/BRAF genotype were identified by univariate and multivariate analyses using the Cox proportional hazards model. The impact of KRAS/BRAF genotype on survival was analyzed using the Kaplan-Meier method. Results: The 5-year survival rate of the cohort was 55.8%. The KRAS and BRAF mutation rates were 38.0 and 2.1%, respectively. BRAF genotype, but not KRAS, was found to be an independent prognostic biomarker (HR = 5.181, P = 0.002) after adjustment for other significant confounding clinicopathological variates: Number of liver metastases (HR = 1.983, P = 0.009), concomitant extrahepatic disease (HR = 1.858, P = 0.014), and surgical margin (HR = 3.241, P < 0.001). BRAF genotype was an independent prognostic biomarker in patients with liver metastases only after metastasectomy (HR = 6.245, P < 0.003). Conclusions: BRAF mutation is an independent prognostic biomarker for colorectal liver metastasectomy.