The MLS side, which fired manager Ryan Nelsen and five of his assistant coaches on Sunday, is facing a hole in its backline with injuries to Steven Caldwell and Justin Morrow.
Canadian coach Benito Floro called up D.C. United defender Nana Attakora to replace Henry. Attakora has six caps (including two starts) for Canada.
The Canadian men are preparing for a Sept. 9 friendly against Jamaica at Toronto's BMO Field.
Toronto (9-9-6) plays in Philadelphia on Wednesday before hosting the Union on Saturday.