Background: Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast. Breast cancer affects the daily lives of many patients and families confronted by changes in health status, lifestyle and roles, leading to impaired quality of life. The aim of the study to assess quality of life (QOL) of patients with breast cancer through four dimensions of quality of life physical, mental, emotional, and social functioning. Research design is an exploratory descriptive design. Subject: A purposive sample composed of 100 adult female patients with breast cancer. Setting: The study was conducted in Ain Shams University Hospitals ,Breast cancer clinic. Tools: structure Interviewing Questionnaire, Europian Organization For Research and Treatment of Cancer QLQ-C30 Instrument(EORTC QLQ-C30) and ( EORTC QLQ - BR23). The study results: The mean age of patients was 52 ±7.1 years. There was statistically significant relation between EROTC QLQ C-30 total global health of life of studied patients and age, residence, previous job (before illness) and smoking. There was statistically significant relation between EROTC QLQ C- 30 functional scales of life of studied patients and age, marital status, type of housing and smoking. There was statistically significant relation between EROTC QLQ C-30 symptom scales of life of studied patients and age, type of housing and smoking. There was statistically significant relation between EROTC QLQ-BR23 symptom scales of life of studied patients and age. Conclusion: there was a moderate quality of life between all studied patients for all dimensions measured for quality of life. This study recommended that: Improving patients quality of life should be the main objective for nurses during their care of patients with breast cancer. Using specific instrument for evaluating quality of life for patients at disease terminal stages.