Background <p>Mechanically ventilated patients in the intensive care unit (ICU) usually develop respiratory muscle wasting atrophy, causing pulmonary dysfunction. The benefits of respiratory muscle training (RMT) on pulmonary function recovery have been demonstrated, but whether it is effective in patients following mechanical ventilation in the ICU has not been proven. This study aimed to evaluate the effectiveness of RMT on lung function and mechanical ventilation duration in ICU patients, addressing the lack of comprehensive evidence on its benefits for mechanically ventilated individuals.</p> Methods <p>This systematic review and meta-analysis was conducted on the databases from PubMed, Cochrane Library, Web of Science, and Embase. The search period was extended to 30th April 2025. Studies included ICU patients receiving RMT, and outcomes such as maximum inspiratory pressure (MIP), forced vital capacity (FVC), and mechanical ventilation duration were analyzed using RevMan software. Heterogeneity was assessed using I² statistics.</p> Results <p>18 randomized controlled trials (RCTs) were included for analysis. RMT significantly improved MIP (SMD: 0.88, 95% CI: 0.53–1.24) and FVC (SMD: 0.32, 95% CI: 0.07–0.58) and reduced mechanical ventilation duration by 0.88 days (95% CI: -1.10 to -0.66).</p> Conclusions <p>Respiratory muscle training enhances lung function and shortens mechanical ventilation duration in ICU patients, supporting its early implementation as a rehabilitation strategy.</p>