Breast cancer (BC) continues to affect the lives of millions of women worldwide. Several members of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) subfamily are involved in tumor progression. Notably, the CEACAM subfamily harbors the already established cancer biomarker CEA, as well as other potential molecular markers. CEACAM19, a recently identified gene belonging to CEACAM subfamily, was discovered and cloned by members of our research group. The present study analyzes, quantitatively, the expression of CEACAM19 and evaluates its clinical relevance in BC. Total RNA was extracted from 143 cancerous and 89 normal adjacent breast tissue specimens. Following reverse transcription, quantitative analysis of CEACAM19 mRNA expression levels was performed via real-time PCR and the comparative Ct (2-∆∆Ct) method. CEACAM19 expression and detailed clinicopathological data were used for extensive biostatistical analyses. CEACAM19 was found to be overexpressed in breast cancer tissue specimens compared to normal tissue counterparts (p=0.013). CEACAM19 mRNA expression status was also associated with clinicopathological features indicative of aggressive behavior and poor prognosis in BC, such as high tumor grade (p=0.031) and high Ki67 proliferative index (p=0.038). A significant negative association was documented between CEACAM19 expression and tumor ER status (p=0.018) as well as patients' menopausal state (p=0.016). Our results suggest that CEACAM19 mRNA expression represents a promising, novel and clinically useful tissue biomarker for breast cancer management.