Kinnear is best known for his roles in the films "Little Miss Sunshine," "As Good As It Gets" and "You've Got Mail."
He is to play Phil's new business partner in the Feb. 8 installment of "Modern Family" called "Me? Jealous?"
"Phil is so preoccupied with impressing his new business partner, Tad, that he doesn't notice what Claire believes is Tad being overtly inappropriate with her," a synopsis said.
Julie Bowen plays Claire and Ty Burrell plays Phil.