Objective To explore the incidence and risk factors of delirium in mechanically ventilated adult patients through meta-analysis， so as to provide a reference for early clinical prevention of delirium. Methods Cross-sectional studies， cohort studies， and case-control studies on the incidence and risk factors of delirium in mechanically ventilated patients were retrieved from The Cochrane Library， PubMed， Embase， Web of Science， China National Knowledge Infrastructure， WanFang Data， VIP and China Biomedical Literature Database. The search period was from database establishment to August 13， 2023. After evaluating the included studies， a meta-analysis of incidence and risk factors was conducted using Stata 17.0. Results A total of 25 studies were included， including 5 936 mechanically ventilated patients. The incidence of delirium in mechanically ventilated patients was 0.42［ 95%CI（ 0.34， 0.50）］. Meta-analysis revealed that risk factors for delirium included advanced age［ OR=1.15， 95%CI（ 1.07， 1.24）］， high Acute Physiology and Chronic Health EvaluationⅡ（ APACHE Ⅱ） scores［ OR=1.40， 95%CI（ 1.24， 1.58）］， prolonged mechanical ventilation ［OR=1.30， 95%CI（ 1.16， 1.45）］， use of sedatives［ OR=1.88， 95%CI（ 1.07， 3.29）］， hypoxemia［ OR=4.09， 95%CI（ 1.77， 9.45）］， prolonged length of ICU stay［ OR=1.18， 95%CI（ 1.04， 1.35）］， sleep deprivation ［OR=12.38， 95%CI（ 4.61， 33.22）］， pain［ OR=2.02， 95%CI（ 1.85， 2.21）］， physical restraints［ OR=2.79， 95%CI（ 1.57， 4.98）］， history of drinking［ OR=2.42， 95%CI（ 1.45， 4.05）］， and history of hypertension ［OR=1.78， 95%CI（ 1.44， 2.20）］. Conclusions The incidence of delirium is relatively high among mechanically ventilated patients. Advanced age， high APACHE II score， prolonged mechanical ventilation， use of sedatives， hypoxemia， prolonged length of ICU stay， sleep deprivation， pain， physical restraints， history of drinking， and hypertension are risk factors for delirium in mechanically ventilated patients. Early prevention， identification， and implementation of effective preventive measures should be based on the patient's condition and risk factors to reduce the incidence of delirium in mechanically ventilated patients.