Breast cancer is the most common gynecological malignancy in the world. In Egypt, it ranks the first among female malignancies with incidence of 37.7%. Over the last decades, the integration of prognostic and predictive markers in treatment decisions has led to more individualized and optimized therapy. NY-BR-1 antigen has been shown to be frequently expressed in breast cancers. The study aimed to assess the tissue expression of NY-BR-1 antigen and serum IgG antibody to this antigen in Egyptian breast cancer females. The study was conducted on 60 females (10 healthy, 10 having benign breast lesions, 40 with malignant breast cancer). NY-BR-1 Ag expression was evaluated by immunohistochemistry and anti-NY-BR-1 IgG was assessed by ELISA. Results revealed a significant difference in NY-BR-1 Ag expression between benign and malignant breast cancer patients. There was a significant correlation between NY-BR-1 antigen expression and estrogen receptor's status (P = 0.019), stage of the disease (P = 0.008), menopausal status (P = 0.008), lymph node involvement (P = 0.022) and anti-NY-BR-1 IgG (P = 0.032) among the studied individuals. In addition, there was a statistically significant increase in anti-NY-BR-1 IgG O.D. results among malignant breast cancer group. It is correlated with tumor type (P < 0.001) and progesterone receptor status (P = 0.038). In conclusion, our work may represent a step towards identification of a new prognostic marker specific for breast cancer.