Gad has signed on to play Kenny, a neighbor of the Dunphys, who bases all of his life decisions on Phil, played by Ty Burell, and worships the ground he walks on.
Gad currently stars as Elder Cunningham in The Book of Mormon, a role that earned him a 2011 Tony Award nomination. He has also been seen on Broadway in The 25th Annual Putnam County Spelling Bee and is known for his television work, which includes "The Daily Show" and "Back to You," among others.
"Modern Family" will return to ABC with a one-hour season premiere Sept. 21 and air Wednesday nights at 9 PM ET.