Background: Breast cancer is now regarded as the main health concern worldwide and among Egyptian women. Addressing the unfulfilled needs of the women with mastectomy is essential as neglecting their needs during different stages of the treatment have a negative impact on the women's health system. Aim: evaluate the effect of structured training program on health needs and practices of women undergoing modified radical mastectomy. Design: A quasi experimental research design (pre and post-test) was utilized. Setting: the general surgery Departments and outpatient breast clinic at Oncology and Nuclear Medicine Center affiliated to Ain Shams University Hospitals. Subjects: A purposive sample of 120 women. Tools for data collection: 1) A structured interview questionnaire; it included three parts: (a) Socio-demographic characteristics; (b) Medical history; (c) Women's Health Needs. 2) An observational checklist to evaluate practices of the studied women. Results: The study revealed a statistical significant difference between total needs pre / post and follow up the structured training program implementation with p <0.001. As well there were a statistical significant differences between pre / post and follow up structured training program implementation among the studied women's satisfactory practices level with p <0.001. Conclusion: It concluded that, structured training program had a positive effect on meeting health needs and improving practices level. Recommendation: Conduct complete health assessment & regular follow – up for all women after mastectomy to identify unmet needs and early detection of the complications.