Globally, breast cancer incidence is on the rise, especially in developing countries and it is the most diagnosed cancer among women in Kenya. For the prevention and treatment, knowledge on early detection and risk factors is very important, however this has not been assessed among women of reproductive age attending Longisa County Referral Hospital Bomet County, Kenya. The study adopted a cross-sectional hospital based design to assess the knowledge on early detection and risk factors to breast cancer among 194 women of reproductive age (15-49 years). Purposive sampling was used to select respondents. Semi structured questionnaire was used to collect data from the study participants. Statistical package for social sciences (SPSS) version 21 was used for data entry, which allowed for analysis using descriptive and inferential statistics. The majority of the respondents have heard about breast cancer 182(93.8%). However, 56 (30.8%) knew about Breast self-examination (BSE) and among these only 44(79%) practiced Breast self-examination (BSE). Those respondents who practiced once a month as recommenced were 23(52.4%).High proportion pointed out that they didn’t have any breast problem 17(37.84%).This study shows that there is poor knowledge on risk factors to breast cancer and poor practice of Breast self- examination (BSE). There is a need for those who provide direct health care to disseminate relevant information to women on breast cancer risk factors and practices such as BSE for prevention and early detection.