Objectives: The aim of this study was to assess the levels of Y-box binding protein 1 (YBX-1) and interleukin 6 (IL-6) in the sera of metastatic and non-metastatic breast cancer patients (BC), investigate their clinicopathological significance and to analyze their potential use as biomarkers of breast cancer metastasis. Methods: The study included ninety subjects sub-grouped equally into metastatic BC, non-metastatic BC and healthy volunteers. Serum YBX-1 and IL-6 were quantified using ELISA technique while CA 15-3 was quantified using IRMA kit. Clinical data were collected from patients' records. Results: YBX-1 (p < 0.001), IL-6 (p < 0.001) and CA15-3 (p = 0.017, 0.001) were significantly elevated in metastatic and non-metastatic BC patients compared to healthy controls, however, only YBX-1 (p < 0.001) and IL-6 (p < 0.001) showed a significant difference with cancer metastasis. Generally, YBX-1 and IL-6 were correlated with worse histological grade and late clinical stage in breast cancer patients and they were also associated with axillary lymph nodes involvement and positive vascular invasion in metastatic BC patients. Serum YBX-1 and IL-6 levels were positively correlated to each other (r s = 0.615, p < 0.001) and they showed high sensitivity and specificity compared to CA 15-3 (p < 0.001 and p = 0.004 for YBX-1 and IL-6 respectively) for predicting cancer metastasis. Conclusions: Serum YBX-1 and IL-6 are potential biomarkers of breast cancer patients with significant correlation with bad clinicopathological characteristics. Serum YBX-1 and IL-6 have superior sensitivity and specificity compared to CA15-3 and can serve as potential follow up and prognostic markers.