Objective To explore risk factors for ventilator-associated pneumonia (VAP) following cardiac surgery in adults. Methods Medical records of adult patients undergoing cardiac surgery through sternotomy in a hospital between January 2017 to May 2021 were collected retrospectively. Patients with VAP after surgery were selected as case group, case-control matching was conducted according to 1 ∶1 matching. Univariate and multivariate logistic regression analysis were performed for the risk factors of VAP. Results A total of 5 919 cardiac surgery adult patients used ventilators after operation, 766 of whom used ventilator for more than 48 hours. 62 patients had VAP, incidence was 1.05%, 8.03 cases/1 000 mechanical ventilation days, and 61 cases were successfully matched. Multivariate analysis showed that pre-operative creatinine≥1.1 mg/dL, duration of operation≥7.33 hours and post-operative disturbance of consciousness were independent risk factors for VAP after cardiac surgery in adults. The pathogen of infection was mainly Gram-negative bacteria (54 strains, 90.0%), Acinetobacter baumannii had the highest isolation rate (24 strains, 40.0%). The risk for gastrointestinal hemorrhage, nasogastric tubing and acute kidney injury in VAP patients significantly increased, and the length of ICU stay, hospitalization cost and mortality significantly increased (all P < 0.01). Conclusion Improving renal function before operation, shortening duration of surgery and reducing post-operative disturbance of consciousness can reduce the incidence of VAP after cardiac surgery in adults.