Noninvasive biomarkers are urgently needed for detecting breast cancer as early as possible since the risk of recurrence, morbidity, and mortality is closely related to disease stage at the time of primary surgery. There are currently no such biomarkers in clinical use as a diagnostic tool. Proteomic analysis of protein expression patterns in body fluids has potential for use in identifying biomarkers of breast cancer. The aim of this study was to compare protein expression levels in the sera of primary breast cancer patients and healthy controls. An antibody microarray tool with 23 antibodies immobilized on nitrocellulose slides was used to determine the levels of acute phase proteins, interleukins, and complement factors in the sera of 101 study participants (49 women with primary breast cancer and 52 healthy age-matched controls). Statistical analysis of reaction intensities identified 6 proteins that showed significantly (p < 0.05) different levels in breast cancer patients vs. healthy subjects. The neural network distinguished cancer patients from controls with a sensitivity of 69% and a specificity of 76%. Thus, antibody microarray analysis could be used as a tool for the development of improved diagnostics and biomarker discovery for breast cancer patients. Further validation of the results and de novo screening of new biomarkers could facilitate the early diagnosis of breast cancer.