Watt will host the show, with musical guest Luke Combs, the day before Super Bowl LIV.
"SNL!!!! I can't even pretend to hide my excitement about this haha! This is something truly special and I am extremely grateful for the opportunity from Lorne and everyone involved at @nbcsnl," Watt tweeted. "New York City let's have some fun!!!"
The three-time NFL Defensive Player of the Year missed eight games this season with a torn pectoral muscle but returned to play in Houston's two playoff games.
Watt not only appeared in the movie "Bad Moms" in 2016, he also co-hosted the CMT Music Awards that year.