Hosted by Cat Deeley, the two-hour broadcast will feature the top 10, who will be joined by the "So You Think You Can Dance" All-Stars. Harris will judge the contestants alongside series resident judges Nigel Lythgoe and Mary Murphy.
"So You Think You Can Dance" has traveled across the country in search of dancers who represent the best in America. Contestants work with top choreographers and are then judged on multiple styles of dance.
Harris, who most recently hosted the 2011 Tony Awards, has been seen on Broadway in Assassins, Proof and Cabaret. He also starred in the New York Philharmonic production of Company. The performer is the winner of two 2010 Emmy Awards and was nominated for his work on the CBS series "How I Met Your Mother."
"So You Think You Can Dance" airs Wednesday and Thursday nights at 8 PM ET on Fox.