Introduction: The nutritional status has been related to breast cancer risk factors as well as to cancer treatment morbid mortality. Thus, its assessment is important for developing strategies for the promotion of nutritional status and breast cancer outcome. Material and Methods: Several different methods used for nutritional assessment in breast cancer patients undergoing therapy were used, including subjective global assessment (SGA), body mass index (BMI), and biochemical analysis (BA). The occurrence of complications during breast cancer treatment versus the nutritional status was assessed. Results: We followed 86 women with age range 18-76 years. Most patients were considered malnourished (65%). A good number of patients experienced complications during breast cancer treatment, and associated with nutritional status. Conclusion: In breast cancer women undergoing therapy, the prevalence of under nutrition was high. There were the effects of poor nutrition or undernutrition on clinical outcomes of breast cancer.