Patients with sickle cell anemia may require repeated red cell transfusion, putting them at risk for minor blood group alloimmunization and the development of delayed hemolytic transfusion reactions. Although Streptococcus pneumoniae is the most common cause of life-threatening infection in patients with sickle cell anemia, those who have been recently hospitalized are at risk for infection with resistant hospital-associated organisms, and blood transfusion may put the patient at risk of infection with transfusion-associated organisms such as Serratia marcescens and Yersinic enterocolitica. We recently cared for an adolescent with sickle cell anemia who presented to the emergency department with a severe, delayed hemolytic transfusion reaction and Serratia marcescens infection. The patient had been discharged from the hospital five days previously, and had been transfused and treated with antibiotics while hospitalized. In addition to demonstrating the potential severity of delayed hemolytic transfusion reactions, our case illustrates the importance of providing relatively broad-spectrum antibiotic coverage to patients with sickle cell anemia and possible infection who have recently been hospitalized.