Breast cancer is the most commonly diagnosed cancer in women and the second leading cause of cancer-related death worldwide. Positive family history increases the likelihood of developing this disease. As late-stage presentation and poor survival rates are associated with a lack of knowledge about breast cancer and its screening methods, this study aimed to evaluate the knowledge of Lebanese women with first-degree relatives who were diagnosed with breast cancer. In this cross-sectional study, 200 women with a positive family history accompanying their relatives to oncology clinics or the infusion center at the American University of Beirut Medical Center, completed an online survey after institutional review board approval was granted. Demographic information and answers to questions related to breast cancer risk factors, warning signs, and screening techniques were collected and analyzed using descriptive statistics and chi-square tests. Eighty-one percent of the study participants agreed that a history of breast cancer is associated with a higher disease risk. The smaller portions were aware of other potential risk factors, such as hormone replacement therapy, alcohol consumption, late menopause, early menarche, and overweight and sedentary lifestyles. Also, 93% to 96.5% of the participants recognized breast self-examination and mammography as useful tools for early detection. Furthermore, younger participants who reached university level and were employed had more insights into breast cancer. Breast cancer knowledge and early diagnosis are key elements in preventing late presentations and reducing the associated morbidity and mortality. Further educational and awareness campaigns should be conducted in Lebanon to improve women knowledge of breast cancer.