Abstract Chest wall deformities, including pectus excavatum, can complicate cardiac operations by impeding sternal entry and cardiac exposure and by affecting cardiac hemodynamic performance. We describe a patient with Marfan syndrome who underwent elective replacement of an aortic root aneurysm. The patient required a simultaneous, unplanned, emergent repair of her severe pectus excavatum because of hemodynamic instability after sternal closure. The success of this procedure suggests that emergent single‐stage repair of pectus excavatum should be considered when median sternotomy closure precipitates hemodynamic instability in such patients.