Background: Breast cancer is one of the leading causes of death among cancer patients in Saudi Arabia. It is known that nurses play a key role in promoting breast cancer awareness among women in any society. Nurses in primary health care centres (PHCC) have more direct contact with general population. This study aimed to investigate nurse knowledge of breast cancer and practice of early screening in PHCC in Jeddah city. Methods: A cross-sectional study was conducted using a self-administered questionnaire to assess the general knowledge of breast cancer, risk factors, and practice of 210 PHCC nurses. Data were analysed using SPSS v.16. Results: The mean age of the PHCC Nurses was 36.9 (SD ${pm}8.6$). Only 11% percent scored <50% of the total score for general epidemiological knowledge on breast cancer, about 35% scored <50% of the total score for breast cancer risk factors. Sixty seven percent scored >75% of the total score on breast cancer signs. Majority of nurses 62.8% practiced BSE, but only 4% practiced regularly every month. Some 28% practiced once per year. About 81% of the nurses had not had a clinical breast examination and only 14% had had a mammography. The results of the study failed to show any correlation between the knowledge scores with age, education, year of experience, family history of BC and marital status of the nurses. Conclusion:The results from the study reflect that there is a need to provide continuing nursing education programmes for PHCC nurses to improve their breast cancer knowledge and practice.