Background: Malnutrition caused by cancer is a prevalent problem in patients with cancer. This study aimed to evaluate the nutritional status of cancer patients undergoing chemotherapy who referred to Vasei Hospital, Sabzevar, Iran. Methods: This descriptive-sectional study was conducted on 124 adult patients (older than 18 years of age) with cancer who had referred to the Oncology Ward of Vasei Hospital, Sabzevar, Iran. Followed by obtaining a consent letter and filling out the demographic questionnaire, the participants’ height and weight were measured in minimum clothing without shoes based on the standard method. Later, the nutrient intake data were collected using the 2-day food intake record at the beginning and end of the chemotherapy. Nutrition IV Software was applied to evaluate the received nutrients. Results: In this research, the mean body mass index of patients was lower at the end than the beginning of chemotherapy (P = 0.001). Mean of serum albumin and total protein were normal at the beginning of the study, which was significantly reduced at the end of study (P = 0.01 and 0.01). Mean of energy, macronutrients, and micronutrients intake indicated a significant reduction from the beginning to the end of treatment (P < 0.05). Conclusion: Findings of this study showed that the mean of serum albumin, total protein and energy, macronutrients, and micronutrients intake indicated a significant reduction from the beginning to the end of treatment in this research.