Objectives: The occurrence of mediastinitis after cardiac surgery remains a rare and severe complication associated with poor outcomes. Whereas bacterial mediastinitis have been largely described, little is known about their fungal etiologies. We report incidence, characteristics and outcome of post-cardiac surgery fungal mediastinitis. Methods: Multicenter retrospective study among 10 intensive care units (ICU) in France and Belgium of proven cases of fungal mediastinitis after cardiac surgery (2009-2019). Results: Among 73,688 cardiac surgery procedures, 40 patients developed fungal mediastinitis. Five were supported with left ventricular assist device and five with veno-arterial extracorporeal membrane oxygenation before initial surgery. Twelve patients received prior heart transplantation. Interval between initial surgery and mediastinitis was 38 [17-61] days. Only half of the patients showed local signs of infection. Septic shock was uncommon at diagnosis (12.5%). Forty-three fungal strains were identified: Candida spp. (34 patients), Trichosporon spp. (5 patients) and Aspergillus spp. (4 patients). Hospital mortality was 58%. Survivors were younger (59 [43-65] vs. 65 [61-73] yo; p = 0.013), had lower body mass index (24 [20-26] vs. 30 [24-32] kg/m(2); p = 0.028) and lower Simplified Acute Physiology Score II score at ICU admission (37 [28-40] vs. 54 [34-61]; p = 0.012). Conclusion: Fungal mediastinitis is a very rare complication after cardiac surgery, associated with a high mortality rate. This entity should be suspected in patients with a smoldering infectious postoperative course, especially those supported with short-or long-term invasive cardiac support devices, or following heart transplantation.< Réduire