Patients with the most common advanced human cancers such as lung, breast, uterus, and cancers of the digestive system almost always develop bone metastases, with painful and untreatable consequences. This study aimed to determine the prognostic implications of the neutrophil/lymphocyte (N/L) ratio in the peripheral blood of patients with malignant bone metastasis. Study participants were identified from a prospective cohort of cancer patients with bone metastasis. Data for the N/L ratios were obtained from clinical and pathological records and were analyzed together with other known prognostic factors in the multivariate and univariate analyses. The results showed the average N/L ratio of all 497 patients to be 4.25±2.44 (range 0.54-45.50 years). Multivariate analysis revealed that tumor type and a high N/L ratio were significantly associated with poor prognosis. For the high N/L ratio group, the estimated hazard ratio of death was 1.348 [95% confidence interval (CI), 1.062-1.712] compared with the low N/L ratio group. The average N/L ratio of the 225 patients in the surgery group was 2.79±2.46 (range 0.77-22.75 years). Multivariate analysis revealed that a preoperatively high N/L ratio (P=0.013; HR=2.945; 95% CI, 1.256-6.906) was significantly associated with poor prognosis after bone metastasis in the surgery group. In conclusion, the N/L ratio was confirmed to be an independent prognostic factor in patients with bone metastasis. Thus, the N/L ratio may serve as a clinically accessible and useful biomarker for patient survival.