Objective: In this study, we investigated the effects of nutritional support on the quality of life of cancer patients, determined nutritional deficiencies, eliminated it at the earliest, and established a built-in system to prolong patient survival. Material and Methods: We included 459 patients admitted to the medical oncology outpatient clinic, diagnosed with cancer and receiving chemotherapy; 59 of 459 patients were diagnosed with malnutrition in the study using the Nutritional Risk Screening (NRS) 2002 nutritional status scale. Appropriate enteral nutrition support was provided to the patients, and control evaluations were made four times at intervals of 28 days. In these controls, information on the height, weight, and the right and left middle arm circumference of the patients was recorded. Along with the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-30 (EORTC QLQ-30) Quality of Life Scale, the Hospital Anxiety and Depression Scale was also used. Results: A statistically significant difference was found in the NRS 2002 scores of the patients regarding the adequacy of intake, protein and calorie requirement, functional status, and the symptom scale. The anxiety and depression scores of the patients decreased in all the controls, and the most noticeable decrease occurred at the end of the third control. Conclusion: Evaluating malnutrition and providing adequate nutritional support to cancer patients improves body composition and the quality of life by reducing anxiety and depression.