Background: Breast cancer is one of the most frequent cancers and the leading cause of death globally. In Egypt, it accounts for 18% of all cancer cases. Objective: In order to assess its clinical value as an early diagnostic marker, the current study examined circulating cell-free mitochondrial DNA (Mt.DNA) detected by RT-PCR in breast cancer patient samples. Subjects and Methods: 25 breast cancer patients and 15 patients with benign masses participated in this study. Patients were selected from Ain-Shams University Hospitals' outpatient clinics and surgery department. The results of these patients were compared with a control group of 10 age-matched healthy persons. For the purposes of determining CEA, CA 15.3, and Mt.DNA, blood samples were obtained. Results: The combined use of Mt.DNA and CA15.3 or CEA, raised the diagnostic sensitivity in discriminating patients with breast cancer from non-cancer patients to 100%, with 96% specificity, 96% PPV, 100% NPV and 98% efficacy. Conclusion: Our research showed that, as compared to women with benign breast illnesses and healthy controls, breast cancer patients have considerably reduced Mt. DNA levels. Mt. DNA levels were also much lower in stage I breast cancer than in benign conditions and healthy individuals, suggesting its potential for use as an early marker.