Migratory songbirds transport hard-bodied ticks (Acari: Ixodidae) into Canada during northward spring migration, and some of these bird-feeding ticks harbor a wide diversity of pathogenic microorganisms. In this study, we collected a nymphal Ixodes affinis Neumann from a Common Yellowthroat, Geothylypis trichas (Linnaeus), at Ste-Anne-de-Bellevue, Québec, and it was infected with the Lyme disease bacterium, Borrelia burgdorferi sensu lato (s.l.) Johnson, Schmid, Hyde, Steigerwalt & Brenner. Using PCR on this tick extract and DNA sequencing on the borrelial amplicons, we detected B. burgdorferi sensu stricto (s.s.), a genospecies that is pathogenic to people and certain domestic animals. In addition, we collected an I. affinis nymph from a Swainson's Thrush, Catharus ustulatus (Nuttall), at Toronto, Ontario, and a co-feeding nymphal blacklegged tick, Ixodes scapularis Say, tested positive for B. burgdorferi s.s. These bird-tick findings constitute the first reports of I. affinis in Ontario and Québec and, simultaneously, the first report of a B. burgdorferi s.l.-infected I. affinis in Canada. Since Neotropical and southern temperate songbirds have a rapid flight pace, they are capable of transporting ticks infected with B. burgdorferi s.l. hundreds of kilometres to Canada. Healthcare professionals should be cognisant that migratory songbirds can transport diverse genotypes of B. burgdorferi s.l. into Canada from southern latitudes that may be missed by current Lyme disease serological tests.