Hornibrook announced his plan on Instagram, posting a photo of himself with FSU head coach Willie Taggart and a caption that expressed excitement for the move.
The 22-year-old Hornibrook announced his decision to leave the Badgers last month.
Florida State was thin at quarterback entering the 2019 season. Deondre Francois, who played in 11 games during the 2018 campaign, was dismissed from the program last month.
The Seminoles also have James Blackman and Jordan Travis as quarterbacks on the roster. Blackman played in three games last season while Travis is a transfer from Louisville who has not yet been granted eligibility to play in 2019, as per Adelson.
Hornibrook, who has one year of eligibility remaining, started the past three seasons for Wisconsin. He threw for 5,438 yards, 47 touchdowns, and 33 interceptions in that span. He is scheduled to graduate in May, and thus will be eligible to play this fall.
During the 2018 campaign he led the Badgers to an 8-5 record with 1,532 passing yards, 13 touchdowns, and 11 interceptions.