Background: the examination of the Breast is regarded as the secondary method of breast cancer protection which must be done by all females during the age 20 years and above. Aim: To assess knowledge and attitude level of females secondary school student’s towards breast self examination (BSE). Subject and method: Cross-sectional study design involved 1000 female student in secondary school in Mosul city .The study started from (1st March till 1st June) 2019, lasting for about (3 months ) by using a self-administer standardized questionnaire include knowledge and attitudes toward , source of knowledge Result: the study revealed that grand mean assessment value regarding BSE general information was 2.09 just above the (cut – off point = 2). The main source of knowledge was health professional (32.3%), followed by TV and social media (27.6%). Nearly two third of study sample had positive attitude to consult doctor and period of consultation within one week with mean score 2.3 and 2.4 respectively. In general the mean score assessment value of attitude toward BSE among study sample was below the cut of point 1.7. Recommendation: Provision of intensive educational program to secondary school students by health professional and encourage school teachers to teach and complete educational curriculum which focus to BSE and take attention to the subject to increase awareness and improve attitude toward it.