The Whitecaps officially announced Montero's signing on Wednesday, and said he will join the club on a one-year loan from CSL side Tianjin Teda.
Minnesota United have signed U.S. international midfielder Josh Gatt, the club announced on Wednesday.
New York City FC have signed winger Maximiliano Moralez from Leon as their third Designated Player.
Toronto FC fell just short of its goal of MLS Cup in 2016. Now the Reds must pick themselves up and prove they can contend year in and year out.
Dempsey, 33, missed the end of the 2016 season after being diagnosed with an irregular heartbeat last August.
The 19-year-old Venezuelan, only moved to the Premier League club on British transfer deadline day on Jan. 31.