Harlequin Ducks (Histrionicus histrionicus) are a relatively rare species in the Canadian Maritime Provinces. Recent confirmed breeding records are restricted to northern New Brunswick. Sightings of small numbers of birds during the molting and staging periods occur in all three provinces. It is estimated that New Brunswick supports as many as 200 wintering Harlequin Ducks, and almost 600 winter off the coast of Nova Scotia, although due to the extent of coast and occasional sightings of Harlequin Ducks from previously unknown locations, it is likely that these are minimum estimates, particularly for Nova Scotia. Few trend data are available in the Maritimes, but available information suggests an increase in the last five years. Hunting, both intentional and unintentional, still occurs; hunter education and enforcement to stop the take of this species could be worthwhile. Coastal development, including vacation home building and aquaculture sites, are occurring in places where Harlequin Ducks winter. There is a general need to monitor the impacts of these developments on local Harlequin Duck populations.