Objective: To explore the correlation between nutritional status, chemotherapy adverse reactions, and quality of life in gastric cancer patients undergoing chemotherapy. Methods: A total of 300 gastric cancer chemotherapy patients admitted to our hospital from February 2022 to February 2024 were selected as the research subjects. The nutritional status was evaluated using the Nutrition Risk Screening Scale (NRS2002), which was divided into a normal nutrition group (NRS2002<3, n=157 cases) and a nutrition risk group (NRS2002≥3, n=143 cases). Compare the nutritional indicators, chemotherapy adverse reactions, quality of life, and correlation between two groups. Results: The results showed that the levels of hemoglobin (15.86±2.65) g/L, prealbumin (256.43±9.11) mg/L, transferrin (2.47±0.33) g/L, and lymphocyte count (3.05±0.74) × 10⁹/L in the normal nutrition group were higher than those in the nutrition risk group. The grade of chemotherapy adverse reactions was better than that in the nutrition risk group, and the scores of social function (87.93±3.15), emotional function (88.45±3.24), role function (90.51±3.06), physical function (91.23±3.15), and cognitive function (92.03±3.29) were all higher than those in the nutrition risk group (P＜0.05); Pearson correlation analysis showed a negative correlation between nutritional status and chemotherapy adverse reactions, and a positive correlation (P＜0.05) with various dimensions of the Quality of Life Scale (QLQ-30) for cancer patients. Conclusion: Patients with gastric cancer undergoing chemotherapy have a higher risk of malnutrition, which is negatively correlated with chemotherapy adverse reactions and positively correlated with quality of life. Clinical attention should be paid to this and effective intervention measures should be taken to reduce chemotherapy adverse reactions and improve quality of life.