Aim <p>This study aimed to explore the effect of frailty on postoperative complications in older patients with joint disorders and to examine the trajectory of frailty changes within three months post-surgery.</p> Methods <p>Older patients who were admitted for joint surgery from July to December 2023 were selected as study subjects. Data collected included general patient information, frailty scores, Age-adjusted Charlson Comorbidity Index (ACCI), Barthel Index and postoperative complications within 30 days after surgery. Frailty assessments were repeated at 1, 2, and 3 months post-surgery.</p> Results <p>The incidence of postoperative complications was 32.5% and Frailty and ACCI were independent risk factors. The area under the curve (AUC) for predicting postoperative complications using frailty, ACCI, and their combination were 0.764, 0.747, and 0.814 respectively, with the combination showing superior predictive ability compared to ACCI alone (<i>P</i> &lt; 0.05). Significant time and group effects were observed in frailty levels at the 1-, 2-, and 3-month postoperative time points between the complication and non-complication groups (<i>P</i> &lt; 0.001), while the time-group interaction effect was not significant (<i>P</i> = 0.643).</p> Conclusion <p>Frailty serves as a valuable auxiliary predictor of postoperative complications in older patients with joint disorders.During the first 1–3 months after surgery, both the complication and non-complication groups exhibited similar declining trends in frailty levels but the former consistently showed higher frailty at each time point. Emphasis on frailty management is essential throughout the perioperative period and key stages of postoperative rehabilitation, with a dual focus on symptom management and frailty intervention in patients with complications to promote recovery.</p>