We report herein a case of Morganella morganii-associated acute purulent pericarditis that developed 3 years after allogenic bone marrow transplantation. The patient was successfully treated with surgical drainage and cefotaxime for 6 weeks. Splenectomy and immunosuppression for chronic GVH-D are likely to have favored the development of this rare infectious complication after BMT. M. morganii should be added to the list of bacteria causing purulent pericarditis, especially in immunocompromised hosts.