A case of dual infection, tularemia and Lyme borreliosis acquired by a single tick bite in northwest Croatia is presented. The patient came from a highly endemic region for Lyme borreliosis, where 45% of the ticks are infected with Borrelia burgdorferi. Clinically, tularemia manifested as the ulceroglandular form, and Lyme borreliosis manifested with arthritis (knee). Both diseases responded well to combined antibiotic therapy.