Radiotherapy is a common cancer treatment, and concurrent nutritional interventions can maintain nutritional status and improve clinical and supportive care outcomes. However, optimal nutritional interventions during radiotherapy are not firmly established. Herein, we assessed the feasibility, safety, and efficacy of dietary counseling interventions without oral nutrition supplements on health outcomes in adults receiving radiotherapy for cancer in a systematic review. Prospective clinical trials that implemented nutritional counseling interventions during radiotherapy were identified from four databases from inception through December 2023. Feasibility, safety, and efficacy were extracted from 32 articles that described 23 randomized and 4 non-randomized clinical trials. The interventions included individualized nutritional counseling (