Breast cancer (BC) is a major public health problem worldwide. It is the second leading cause of death after lung cancer. More than half of patients with BC receive systemic chemotherapy as a form of treatment. They are good at killing cancer cells, but they can temporarily weaken immunity. The damaged to normal cells cause common unpleasant side effects including, nausea, vomiting , fatigue, infection…etc. The body's immune system is designed to fight off and recognize these abnormal cancer cells and kill them. For this reason if BC has been diagnosed, it is of great importance to re-build and keep the immune system in a good fighting condition. The aim of the present study is to evaluate the effect of immune enhancement intervention on clinical outcomes of patients with BC undergoing chemotherapy. The research design was quasi-experimental design. Setting: It was conducted at the clinical oncology department at Nasser Institute hospital(Cairo).Sample: A purposive sample included 100 patients divided into control and study groups. Tools of data collection: Data were collected using structured interview questionnaire, Australia-modified Karn of sky performance status scale, quality of life assessment scale & nutritional assessment sheet including laboratory investigation &tumor markers. The results: Showed that; (60% and 52%) of the study group and (68% and 48%) of control group were married and aged (50 - 70 years old) respectively and there was a highly significant difference existed between the two groups regarding their knowledge, quality of life, performance status for usual activities and nutritional status post intervention which in turn lead to highly significant decrease the tumor biomarkers among study group versus control group P<0.001. Conclusion: Immune enhancement intervention program had statistical significant positive effect on clinical outcomes of patients with BC undergoing chemotherapy. Recommendations: Further study is recommended to conduct the training and teaching of nurses about the immune enhancement intervention program and evaluate its impact on their performance and consequently on patients outcomes on the long run.