The majority of babesia infections in Europe are life-threatening and caused by Babesia divergens and B. bovis. Although Babesia microti has been detected in ticks from Switzerland, few if any cases of babesiosis have been caused by B. microti. This first reported case, diagnosed by serology, DNA detection, and microscopy, is additionally interesting because there appears to be coinfection with the Lyme disease organism, Borrelia burgdorferi.