Objective: To analyze the factors associated with readmission within three months of surgery for gastric cancer and the impact of readmission on patients' long-term nutritional status and quality of life. Methods: This was a prospective cohort study comprising patients who underwent radical gastrectomy in the Department of Pancreatic and Gastric Surgery, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences from October 2018 to August 2019. Patients who failed to complete postoperative follow-up, whose body mass index (BMI) could not be accurately estimated, or who were unable to complete a quality-of-life questionnaire were excluded. The patients were followed up for 12 months. Time to, cause(s) of, and outcomes of readmission were followed up 1, 2 and 3 months postoperatively. BMI was followed up 1, 3, 6 and 12 months postoperatively. Results of blood tests were collected and patients' nutritional status and quality of life were assessed 12 months postoperatively. Nutritional status was evaluated by BMI, hemoglobin, albumin, and total lymphocyte count. Quality of life was evaluated using the European Organization for Research in the Treatment of Cancer (EORTC) Quality of Life scale. The higher the scores for global health and functional domains, the better the quality of life, whereas the higher the score in the symptom domain, the worse the quality of life. Results: The study cohort comprised 259 patients with gastric cancer, all of whom were followed up for 3 months and 236 of whom were followed up for 12 months. Forty-four (17.0%) patients were readmitted within 3 months. The commonest reasons for readmission were gastrointestinal dysfunction (16 cases, 36.3%), intestinal obstruction (8 cases, 18.2%), and anastomotic stenosis (8 cases, 18.2%). Logistic regression analysis showed that preoperative Patient-Generated Subjective Global Assessment score ≥ 4 points (OR=1.481, 95% CI: 1.028‒2.132), postoperative complications (OR=3.298, 95%CI:1.416‒7.684) and resection range (OR=1.582, 95% CI:1.057‒2.369) were risk factors for readmission within 3 months of surgery. Compared with patients who had not been readmitted 12 months after surgery, patients who were readmitted within 3 months of surgery tended to have greater decreases in their BMI [-2.36 (-5.13,-0.42) kg/m2 vs. -1.73 (-3.33,-0.33) kg/m2, Z=1.850, P=0.065), significantly lower hemoglobin and albumin concentrations [(122.1±16.6) g/L vs. (129.8±18.4) g/L, t=2.400, P=0.017]; [(40.9±5.0) g/L vs. (43.4±3.3) g/L, t=3.950, P<0.001], and significantly decreased global health scores in the quality of life assessment [83 (67, 100) vs. 100 (83, 100), Z=2.890,P=0.004]. Conclusion: Preoperative nutritional risk, total or proximal radical gastrectomy, and complications during hospitalization are risk factors for readmission within 3 months of surgery for gastric cancer. Perioperative management and postoperative follow-up should be more rigorous. Readmission within 3 months after surgery may be associated with a decline in long-term nutritional status and quality of life. Achieving improvement in long-term nutritional status and quality of life requires tracking of nutritional status, timely evaluation, and appropriate interventions in patients who need readmission.