Nowadays, the search for new biomarkers of cancer is actual for early diagnostic. The antibodies against antigens associated with tumors arouse an interest as an alternative to the present biomarkers. The alteration of quantity and specificity of antibodies in blood serum indicates processes occurring in the organism, including development of oncologic diseases. The article presents the results of analysis of repertoire of antibodies (immunosignatures) using peptide micro-chips in patients with diagnosis of breast cancer. The study established 119 informative peptides out of 330 034 peptides, presented on the microchip. The binding of antibodies with them demonstrates statistically significant intergroup values (p<0.001). This panel of peptides is effective in discerning sera of patients and healthy donors with high sensitivity and specificity. The evaluation of repertoire of antibodies interacting with panel of synthetic peptides can be used in development of diagnostic tests in case of detection of breast cancer at early stages.