The wild cards were announced as the International Tennis Federation released its full list of official entries for this summer’s Olympic tournaments in London.
Vancouver's Pospisil had previously been named to the Canadian team as the partner for top-ranked doubles player Daniel Nestor.
Wozniak, from Blainville, Que., will also do double duty, as her No. 56 world ranking in singles had already earned her a spot in the women's draw.
That makes Dubois, from Laval, Que., the only new Canadian player being added to the Olympics as part of Tuesday's announcement.
The Canadian team also includes Milos Raonic of Thornhill, Ont., who will compete in men’s singles.
A total of six men and six women per country are allowed to participate in Olympic tennis, with a maximum of four singles players, two doubles teams and two mixed doubles teams per draw. Entries for mixed doubles teams will be taken from those players already competing in singles and doubles.