In view of the fact that breast cancer is the most common cancer among Omani females and since there are no previous studies on breast cancer awareness and the practice of BSE in Oman, this study was performed. Aim: To assess the awareness of breast cancer in the Omani female population in the Muscat governorate in terms of the knowledge of its risk factors, as well as the curability and screening modalities, in order to identify popular misconceptions, current perceptions, and attitudes towards the disease, factors associated with knowledge, sources of information associated with cancer education, and population groups who might benefit from such education. Methods: A multi-component questionnaire including a knowledge scale has been designed and pre-tested for this study. The 57-item knowledge scale includes four subscales containing items covering general, curability, screening, and risk factor knowledge. This cross sectional survey included 2,579 women who were attending secondary (grades 10, 11, and 12) schools, Sultan Qaboos University, and primary care health centers in the Muscat govemorate between May and November, 2006. The study population was classified into five study groups: secondary students, university students, community participants, secondary teachers, and nurses. The majority of the data was obtained through self- or group-administered questionnaires, part of the data was obtained through face-to-face interviews. For assessment of breast cancer awareness, a composite (cumulative) knowledge score and subscale knowledge scores were computed. The results were analyzed using chi-square test, one way analysis of variance (ANOVA), Kruskal-Wallis test, and step-wise logistic regression analysis. Validity and reliability testing of the knowledge scale was done using point biserial correlation and Cronbach's alpha. Results: The internal consistency reliability of the combined knowledge scale was 0.80 and of the four knowledge subscales ranged between 0.54 and 0.79. The mean composite knowledge percent score of the total study population was 38.04% (95% CI 37.3–38.8%). The secondary students had the lowest mean composite knowledge percent score (32.17 + 14.65) and scored lowest in all the knowledge subscales. On the contrary, the nurses had the highest composite knowledge percent score (57.2 + 10.9) and scored the highest in all the knowledge subscales. There was no significant difference between the mean composite knowledge percent score of the university students and the secondary teachers (p= 0.982). Based on a multivariate logistic regression model, higher educational level, mother's higher education level, a known acquaintance with a diagnosis of breast cancer, being informed about breast cancer, and the perception of being well informed are important predictors of knowledge about breast cancer. The prevalence of women practicing BSE was 36.7% (95% CI 34.8–38,6%). Knowledge of breast cancer is positively and significantly associated with an increased likelihood of practicing BSE. Based on a multivariate logistic regression model, age, higher educational level, being informed about breast cancer, a known acquaintance with a diagnosis of breast cancer, and knowledge about breast cancer and its detection methods are important predictors of the practice of BSE. The main barrier expressed across all groups that would prevent or delay women from seeking medical advice was wariness from being examined by a male doctor. The most common sources of information about breast cancer across all groups were the electronic and print media followed by family or friends. Conclusion: Although the majority of this study population was educated, the low level of knowledge about breast cancer among Omani women is evident among all studied groups and a targeted national campaign to improve awareness is an urgent need.