Dietary interventions during chemotherapy hold promise for clinical and supportive care outcomes. We systematically investigated the feasibility, safety, and efficacy of nutritional counseling conducted during chemotherapy. Studies prospectively implemented nutrition counseling during chemotherapy. Articles were identified from three databases-EMBASE, Cochrane Library, and SCOPUS-from inception to 1 October 2024. Feasibility, safety, and efficacy of outcome data were extracted. Among 44 publications, 39 studies recruited 98 ± 80 participants (range 15-360); 38/39 (97%) were randomized controlled trials. One-third (31%) were among patients with breast cancer. Interventions were divided into individualized nutritional counseling ( = 21), nutrition counseling plus exercise ( = 13), and nutrient-specific dietary patterns ( = 10). Many had goals to achieve established nutrition guidelines. Feasibility was high based on attendance at counseling sessions, retention, and/or food log analysis. Overall, there were minimal adverse events related to the interventions. Many studies showed between-group differences favoring the intervention group for body weight (8/24, gain or loss, according to goals), nutritional status (8/9), quality of life (3/10 without and 6/9 with exercise), cancer-related fatigue (7/10), chemotherapy tolerance (6/11), and treatment responses (3/13). In conclusion, nutritional interventions were feasible and safe for patients undergoing chemotherapy and demonstrated preliminary efficacy to improve nutritional status, fatigue, chemotherapy tolerance, and other outcomes.