Background <p>Over 2&#xa0;million cardiac surgeries are performed annually, with significant risks such as systemic inflammation and postoperative pulmonary complications (PPCs). Dexmedetomidine has shown promise in reducing PPCs in thoracic surgeries. This review evaluates its effects on PPCs and respiratory outcomes in cardiac surgery.</p> Methods <p>A systematic search of the PubMed, Embase, Cochrane Library, and Web of Science databases was conducted to include randomized controlled trials comparing intravenous dexmedetomidine and other drugs in terms of respiratory outcomes in adult patients undergoing cardiac surgery. Primary outcome: PPC incidence. Secondary outcomes: PaO₂, PaCO₂, SpO₂, oxygenation index, respiratory index, time to extubation, length of ICU stay, and adverse events. Risk ratios (RRs) and mean differences (MDs) were calculated using random-effects models.</p> Results <p>Sixteen studies comprising 1,668 patients were included in this meta-analysis. The perioperative use of dexmedetomidine was associated with a reduced incidence of overall postoperative pulmonary complications (RR = 0.57; 95% CI: 0.38 to 0.87; <i>P</i> = 0.0078). Additionally, participants who received intravenous dexmedetomidine had a shorter ICU stay (MD = -0.56&#xa0;h; 95% CI: -1.12 to -0.00; <i>P</i> = 0.0480). Furthermore, perioperative dexmedetomidine significantly improved postoperative SpO₂ (MD = 0.46% points; 95% CI: 0.17 to 0.74; <i>P</i> = 0.0018) and respiratory index (MD = -0.16; 95% CI: -0.27 to -0.05; <i>P</i> = 0.0057).</p> Conclusion <p>Perioperative dexmedetomidine may be associated with improved respiratory outcomes in cardiac surgery patients. However, the evidence for reduction in overall PPCs remains limited, and dexmedetomidine may increase the risk of bradycardia. Larger, high-quality RCTs are needed to confirm its safety and benefits.</p>