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.