The former Seinfeld star will play Santa Claus in the latest stage adaptation of Will Ferrell's 2003 hit holiday comedy film.
Ed Asner played the role in the original movie, while Cheers actor George Wendt took on the character in the 2010 Broadway staging.
Beth Leavel also joins Knight in Elf on Broadway as Emily Hobbs, a part originally played by Mary Steenburgen.
Elf premieres at the Al Hirschfeld Theatre on November 9, with further casting announcements to come in the next few weeks.
The play is expected to run through January 6.
Watch a trailer for the film Elf below: