Short title of the paper … Background Breast cancer, the most prevalent health threat to women, showed increased incidence rate in developed countries as compared with developing ones. Circulating microRNAs are among the lately non-invasive acknowledged participants in breast carcinogenic transform. Aim Evaluate the role of plasma miR155 in breast cancer female patients. Methods Plasma miR155 was assessed in 50 female patients with breast cancer and 20 healthy female subjects by quantitative real-time polymerase chain reaction. Expression was correlated with clinicopathological data. Moreover, receiver operating characteristics (ROC) analysis was performed to determine sensitivity and specificity of miR155. Results Plasma miR155 showed significantly higher expression in breast cancer patients compared to controls. Patients without family history of breast cancer showed significant higher expression compared to those with family history of breast cancer. Expression was correlated to higher tumor stage (rho=0.470, p=0.001). ROC curve analysis for miR155 to discriminate breast cancer patients from healthy controls showed AUC value of 0.998, sensitivity and specificity of 98% and 100% respectively. Conclusion Circulating plasma miR155 might be a potential breast cancer blood biomarker facilitating breast cancer diagnosis and likely helpful to monitor disease progression. However future larger cohorts are required to validate the role of miR155 in breast cancer disease.