Over the past two decades there have been significant developments in the fields of laboratory technology, genetics and bioinformatics. These developments have raised the attractiveness of liquid biopsy - a test aimed to detect tumor markers in body fluids. One of the liquid biopsy methods is based on identification of circulating tumor DNA - fragments of DNA originating from the tumor which are evident in the bloodstream - revealing the various tumor characteristics via simple blood tests. This novel approach has several advantages over the traditional biopsy: it is noninvasive and thus more convenient and safer for the patient; it reflects the characteristics of the entire tumor tissue present in the patient's body in a single test; it is performed quickly and safely by a phlebotomist and does not rely on the subjective interpretation of the pathologist. The liquid biopsy is a highly valuable tool for the diagnosis and monitoring of cancer, which can be recruited for the clinical management of breast cancer - the most common malignancy in females which is estimated to affect one in every eight women. In this review we will present the existing and the potential applications of the liquid biopsy in breast cancer patients, regarding the various settings of patient care - diagnosis, treatment and follow-up.