Delayed hemolytic transfusion reactions usually occur as a result of a secondary immune response with maximal hemolysis occurring seven days posttransfusion. We report a delayed hemolytic transfusion reaction in which hemoglobinuria, anemia, and reticulocytosis developed four weeks after transfusion. The incriminated antibody, anti-C, was first detected eight weeks posttransfusion using enzyme-treated red blood cells. We conclude, that in all likelihood, this hemolytic transfusion reaction was due to a primary immune response, this case illustrates the importance of sequential testing in cases of suspected transfusion reactions.