Josh Philippe and fast bowler Ben Dwarshuis also linked to the Washington franchise for the July tournament.
Australia's premier white-ball spinner Adam Zampa is also set to join the Kolkata Knight Riders owned franchise – Los Angeles Knight Riders – while Matthew Wade is another to have signed with an MLC club.
Henriques joins former Aussie T20 skipper Aaron Finch and Marcus Stoinis in signing deals as overseas players for the tournament, with the World Cup-winning duo to join San Francisco Unicorns who have a high performance partnership with Cricket Victoria.
Meanwhile, Mitch Marsh's call up to Australia's Test squad for the World Test Championship Final and Ashes has curtailed his plans to play in the MLC, with the WA allrounder replaced by the likes of Sri Lanka's Dasun Shanaka and Zimbabwe's Sikandar Raza at the Seattle Orcas.
Washington have announced the most overseas signings of the six MLC franchises with Henriques joining South African pair Anrich Nortje and Marco Jansen, Kiwis Glenn Phillips and Adam Milne, and Sri Lankan spinner Wanindu Hasaranga at the Freedom.
Washington Freedom are set for a Sydney Sixers takeover with several Australian stars poised to join their skipper in the inaugural edition of United States T20 tournament