The former Houston Dynamo striker was picked first but may choose to retire before the upcoming season.
Philadelphia's Justin Mapp was also among the 10 selections made by Montreal, which will join Major League Soccer next season.
Ching has won three MLS Cup trophies and recently helped guide Houston to this year's MLS Cup, where the team fell 1-0 to the LA Galaxy. He was limited to just 20 games last season due to injuries, but he still managed to score five goals.
"When you see the list when it comes out, Brian's name sticks out because he's one of the guys on there with multiple championships and he's very experienced," Impact coach Jesse Marsch said. "We were quite surprised that he was on the list."
The 33-year-old has stated that he would like to remain with the Dynamo as the team moves into a new stadium in 2012, but he may have to retire and take a front office job to do so.
Montreal was well aware of the risk in selecting Ching and will likely use him in a future trade as it looks to build a team from the ground up.
"I know that he's expressed he doesn't want to be here, but we would be delighted to get him here. If it doesn't work out that way, then it doesn't. But we think there's value to him and there were still some team in the league that were interested in him," Marsch said.
"But our initial phase was just to now think about what he is as a player and what value he has. When you look at the draft you have to look at it in terms of now building a team and what pieces you want to put in place for your team moving forward but also how to maximize the value of the draft."
Montreal's expansion draft picks
1. Brian Ching, F, Houston
2. Zarek Valentin, D, Chivas USA
3. Justin Mapp, M, Philadelphia
4. Bobby Burling, D, San Jose
5. Jeb Brovsky, M, Vancouver
6. Collen Warner, M, Real Salt Lake
7. Josh Gardner, D, Columbus
8. Sanna Nyassi, M, Colorado
9. James Riley, D, Sounders FC (traded to Chivas USA)
10. Seth Sinovic, D, Sporting KC