Babesiosis has only recently been reported in Canada, but a number of transfusion-transmitted cases of this infection have been reported from the United States. We present a case of transfusion-transmitted babesiosis that occurred in Canada. Canadian physicians must consider babesiosis in the differential diagnosis of patients who experience fever or a hemolytic reaction after blood transfusion. Prompt recognition and treatment are important, because Babesia infections can be severe or fatal in certain risk groups. Better strategies to prevent transfusion-transmitted babesiosis are required.