The data related to BRCA1 germline mutation in Chinese women with familial breast cancer is increasing. However, little is known the frequency of BRCA1 mutations in Chinese women with familial or early-onset breast cancer from Northern China, and few studies are available to investigate the clinicopathological characteristics of BRCA1 tumors in Chinese women. In this study, we detected germline mutations in BRCA1 in a cohort of 139 breast cancer patients who either have a family history of breast cancer (n = 68) or whose tumors are diagnosed at or before the age of 35 (n = 71) from Northern China. A total of 6 deleterious BRCA1 mutations were identified in this cohort, 4 of which (5587-1 del8, 3887 del AG, IVS21 + 1delG, and 2129 ins TG) are novel and one mutation (3478del5) detected in this study was only reported in Chinese population. The frequency of BRCA1 mutations in women with familial or early-onset breast cancer was 5.9% (4/68) or 2.8% (2/71) in this cohort, respectively; but the mutations were detected in 4 of 16(25.0%) familial breast cancer patients whose tumors were diagnosed before the age of 40. Moreover, BRCA1 mutation tumors tended to be high histological grade, and to be negative for ER, PgR, and Her-2 compared with tumors without BRCA1 mutations. Our study suggests that Chinese women with a family history of breast cancer whose tumors are diagnosed before age of 40 would be a suitable candidate for BRCA1 testing; and BRCA1 tumors in Chinese women exhibit an aggressive phenotype.