Platt will guest star on the Oct. 5 episode of the reboot of the late sitcom, NBC announced Thursday.
The actor won rave reviewss for his performance as the title character in Steven Levinson's musical, followed by a boatload of awards. His other credits include the Pitch Perfect movies and the musical The Book of Mormon, in which he made his Broadway debut.
Platt, who's just 23, will bring a younger sensibility to the reboot of what could be a dated comedy. The show is making an attempt to change with the times, though. Star Debra Messing told TV Guide that the show will try to do a better job of LGBT representation in the reboot.
"[When] we did the show, we really focused on LGB...We stopped there at B. I know I wanna continue through the alphabet," she said.
Will & Grace returns Thursday, Sept. 28 at 9/8c on NBC.