Objective To investigate the predictive value of inferior vena cava variability (ΔDIVC) combined with the diaphragmatic-rapid shallow breathing index (D-RSBI) for weaning outcomes in elderly mechanically ventilated (MV) patients. Methods Clinical data from 298 elderly MV patients (age≥60 years) admitted to the ICU of the First Affiliated Hospital of Jinzhou Medical University between January and December 2023 were retrospectively analyzed. According to weaning outcomes (success: extubation without reintubation within 48 hours; failure: reintubation within 48 hours), patients were divided into a success group (n=211) and a failure group (n=87). Bedside ultrasound was used to measure ΔDIVC and D-RSBI. Receiver operating characteristic (ROC) curve analysis and Pearson correlation were employed to evaluate their predictive efficacy. Results The success group showed significantly higher ΔDIVC (25.24±4.48% vs. 20.18±3.24%, P<0.001) and lower D-RSBI (1.61±0.22 vs. 2.20±0.33, P<0.001) than the failure group. For predicting weaning success, ΔDIVC yielded an AUC of 0.813 (sensitivity 78.20%, specificity 65.52%, cut-off 21.5%). For predicting weaning failure, D-RSBI yielded an AUC of 0.918 (sensitivity 89.10%, specificity 89.66%, cut-off 1.85 counts·min?1·mm?1). The combined model achieved an AUC of 0.954 (95%CI 0.930-0.978), significantly outperforming either parameter alone (P<0.05). ΔDIVC and D-RSBI were negatively correlated (r=–0.351, P<0.001). Conclusion The combination of ΔDIVC and D-RSBI significantly improves the accuracy of predicting weaning outcomes in elderly MV patients, providing a reliable basis for individualized clinical weaning strategies.