We report on a 56-year-old woman with a history of splenectomy and surgery of the left hemidiaphragm, who presented with multiple pleural and mediastinal mass lesions. On the basis of the patient's history of splenectomy and missing Howell-Jolly bodies in peripheral blood smears, splenosis was suspected. To confirm the presumptive diagnosis, ferumoxides-enhanced magnetic resonance was performed. As all lesions showed a pronounced signal loss on T2* sequences, the diagnosis of splenosis was made and was further confirmed by scintigraphy. The reported case illustrates that ferumoxides-enhanced magnetic resonance imaging may be a helpful tool for the evaluation of suspected splenosis.