Background: Cancer treatment may relate to appetite reduction and malnutrition, taste alterations, and dish-type preferences during chemotherapy in breast cancer women. Understanding women with cancer knowledge and practices regarding their nutrition is essential. Hence, the study aimed to evaluate the effect of nutritional teaching programs on knowledge, practices, taste alterations, and appetite among breast cancer women undergoing chemotherapy. Subjects and method: Design: A quasi-experimental research design was used with a pre-and post-test. Setting: the research was conducted in the outpatient clinic at Sohag Oncology Institution. Subjects: A convenient sample of all 100 breast cancer women undergoing chemotherapy was included within six months. Three tools were used: Tool (I) women's structured interviewing questionnaire, which included four parts: (a) demographic characteristics; (b) women's medical data, (c) women's nutritional knowledge among breast cancer women undergoing chemotherapy, and (d) women' practices nutritional knowledge among breast cancer women undergoing chemotherapy(pre/post). Tool (II) Chemotherapy-induced taste alteration scale (CiTAS), and Tool (III) Perceptions evaluation related to food intake. Results: There was a positive correlation (P=0.005) between women's knowledge scores and their practical knowledge post-one-month nutritional teaching program implementation. There were evident improvements in women's knowledge and practical knowledge regarding nutrition among breast cancer women undergoing chemotherapy post-nutritional teaching program implementation (P=0.005).  In this study, it was found that slight and significant improvements regarding taste alterations, and appetite among breast cancer women undergoing chemotherapy post nutritional teaching program implementation. Conclusion: The implementation of the nutritional teaching program had a positive effect on improving knowledge, practices, taste alterations, and appetite among breast cancer women undergoing chemotherapy. Recommendations: A nutritional teaching program should be conducted regularly for women undergoing chemotherapy to discuss and teach them different aspects of nutrition and replicate the current study with a larger sample.