Background: Breast cancer (BC) has many risk factors that lead to its diagnosis in premenopause and more common in postmenopause; most of these factors are modifiable; including anthropometric factors and reproductive factors. Objectives: To assess knowledge and its associated factors among physicians in primary healthcare settings in Makkah city about the modifiable risk factors of breast cancer. Subjects and methods: A cross-sectional study was conducted in Makkah Al-Mukarmah city, western area of Saudi Arabia among a sample of primary healthcare physicians working at the PHC centers, belonging to the internal PHC sectors inside the city. A self-administered questionnaire was utilized in the present study. It includes two main sections; background information of the physicians and assessing the knowledge of the participants regarding modifiable risk factors for breast cancer (Contraceptive history, obesity/physical activity, smoking and diet). Results: A total of 150 primary healthcare physicians have participated in the study. More than half of them (58.7%) aged between 20 and 30 years, and 56% were females. The knowledge score ranged between 16 and 30 with a mean±SD of 23.71±3.16. Almost two-thirds of the physicians (68%) had high level of knowledge. Among studied sociodemographic factors, only the degree of job of the participants was significantly associated with knowledge level about BC as the highest score was observed among residents (25.46±1.98) and the lowest among general practitioners (22.27±3.39), p<0.001. Conclusion: most of primary healthcare physicians in Makkah had good level of knowledge regarding breast cancer modifiable risk factors, resident physicians. Their main source of information was the Internet, followed by books and guidelines.