Preserved specimens of the crayfish Cambarus bartonii, Orconectes limosus, and Orconectes virilis from 27 locations in New Brunswick, and O. limosus from Freshwater Lake, Cape Breton Highlands National Park, Cape Breton Island, NS, Canada, were examined for branchiobdellidans. Three species of branchiobdellidans—Bdellodrilus illuminatus, Cambarincola fallax, and Xironogiton instabilis—were identified on C. bartonii. Only branchiobdellidan cocoons were recorded on O. limosus, and only X. instabilis was recovered from O. virilis in New Brunswick. The introduction of O. limosus and O. virilis into New Brunswick does not appear to have simultaneously introduced non-native branchiobdellidans. No branchiobdellidans were found on introduced O. limosus from Freshwater Lake, NS. This work provides the first records of branchiobdellidans occurring in the Maritime Provinces of Canada, and establishes the eastern limit for these ectosymbionts in North America. In addition, one specimen of C. bartonii was found to have a total of 39 B. illuminatus in the branchial chambers, the largest infestation of this species yet recorded.