Objective: To elucidate the clinicopathological differences between breast cancer 1 (BRCA1) and BRCA2 carriers among patients with breast carcinoma. Material and Methods: The present retrospective study explored the demographic and clinicopathological features of 57 BRCA carriers with breast cancer. The age, family history, tumor Ki-67 index, tumor grade, hormone receptor status (estrogen and progesterone), human epidermal growth factor receptor 2 status, tumor T and N Stage, tumor multifocality, and tumor treatment modalities (surgical or adjuvant/neoadjuvant chemotherapy) were recorded for each patient from the hospital automation system. Results: The patients with a median age of 39 (range: 23-68 years) years comprised 35% BRCA1 and 65% BRCA2 carriers. Higher median Ki-67 index was revealed for the BRCA1 group than for the BRCA2 group (40% vs. 80%, p=0.006). The proportions of patients with estrogen receptor (+) and progesterone receptor (+) tumors were 35.0% and 35.0%, respectively, in the BRCA1 group, whereas 75.7% and 73.0%, respectively, in the BRCA2 group (p value 0.003 and 0.005, respectively). The BRCA1 group demonstrated significantly higher proportion of triple-negative patient rate as compared to the BRCA2 group (21.6% vs. 55.0%, p=0.011). Multivariate logistic regression analysis conducted with the Ki-67 index, estrogen receptor status, progesterone receptor status, and triple-negative disease status identified the Ki-67 index as the only independent predictive factor that could distinguish the BRCA1 from the BRCA2 mutation. A high Ki-67 index (>45%) was correlated with the BRCA1 mutation (odds ratio: 0.970, 95% confidence interval: 0.943-0.999, p=0.044). Conclusion: A high Ki-67 index is more frequently prevalent in BRCA1 carriers than in BRCA2 mutation carriers among patients with breast cancer.