Background <p>Patients undergoing peritoneal dialysis are at high risk of infection, which significantly impacts morbidity and mortality. This retrospective study aimed to evaluate the association of thymopentin use with infection risk, immune function, and inflammatory markers in peritoneal dialysis patients.</p> Methods <p>Clinical data from 100 patients undergoing peritoneal dialysis were collected and analyzed. According to the treatment regimens received, patients were divided into a control group (standard therapy) and a thymopentin group (standard therapy combined with thymopentin). Thymopentin was administered subcutaneously at a dose of 10&#xa0;mg daily for the first 5 days, followed by 10&#xa0;mg three times per week (Monday, Wednesday, and Friday) for 23 consecutive weeks. Patients were followed for a total of 48 weeks. Infection rates, immune function, and levels of inflammatory markers were compared between the two groups.</p> Results <p>The thymopentin group demonstrated a lower infection incidence than the control group (0.73 vs. 1.00 per person-year). Thymopentin use was associated with significantly reduced overall infection rates (<i>P</i> &lt; 0.001) and peritonitis (<i>P</i> = 0.031). Multivariate analysis confirmed a lower infection risk (HR = 0.54, 95% CI: 0.30–0.95; <i>P</i> = 0.034). Inflammatory markers showed favorable changes: interleukin-2 receptor (IL-2R) levels increased at 12 and 24 weeks (<i>P</i> = 0.002 and 0.020), interleukin-6 (IL-6) decreased at 12 weeks (<i>P</i> = 0.036). Serum albumin rose at both time points (<i>P</i> = 0.023 and 0.040). No significant changes were observed in CD3⁺/CD4⁺ or CD8⁺ T cells or the CD4/CD8 ratio.</p> Conclusion <p>Thymopentin use was associated with reduced infection risk and favorable changes in inflammatory and nutritional markers among peritoneal dialysis patients. These findings suggest potential benefits of Thymopentin in this population.</p> Clinical trial number <p>Not applicable.</p>