Background Liver metastases from breast cancer are associated with poor prognosis, and treatment options are usually restricted to palliative systemic therapy. The impact of liver resection on metastasis remains controversial. The aim of this study is to investigate whether liver resection can offer better survival outcomes in cases of isolated liver metastases from breast cancer. Methods We conducted a nationwide cohort study using a claims dataset from Taiwan’s National Health Insurance Research Database (NHIRD). We identified all patients with breast cancer (diagnostic code ICD-9: 174.x) from the Registry for Catastrophic Illness Patient Database (RCIPD) of the NHIRD who underwent mastectomy between January 1, 2000, and December 31, 2008. Patients with other malignancies (history, initially, or during follow-up), those with a history of metastasis prior to or at initial admission for mastectomy, and those without liver metastases were excluded. Patients with other metastases between mastectomy and liver metastasis and those who died at first admission for liver resection were also excluded. All patients were followed up until December 31, 2013, or withdraw from the database because of death. Results Data were analyzed for 1,116 patients who fulfilled the inclusion criteria (resection group: 89; non-resection group: 1,027). There were no differences in age, Charlson Comorbidity Index, or major coexisting diseases except renal disease between two groups. Kaplan–Meier analysis demonstrated that the liver resection group had significantly better overall survival (OS) than the non-resection group. (1-year: 96.6% vs. 52.3%, 2-year: 86.8% vs. 35.4%, 3-year: 72.3% vs. 25.2%, 5-year: 51.6% vs. 16.9%, respectively, p<0.001). Cox analysis revealed that the liver resection group exhibited a significant improvement in patient survival (hazard ratio [HR] = 0.321, 95% confidence interval [CI]: 0.234–0.440, p<0.001). Conclusion These findings indicate that liver resection may offer better survival benefit in patients with breast cancer who develop new liver metastases post mastectomy.