McFadden, No. 49 in the ESPN 300, becomes the ninth ESPN 300 pledge for the Seminoles, who currently have the fourth-ranked 2015 recruiting class following a No. 3-ranked finish in 2014.
McFadden, who made his only official visit to Florida State, picked the defending national champions over Georgia.
The 6-foot-3, 195-pound McFadden is the No. 5-ranked cornerback in the 2015 class, and will fill a big need for the Seminoles with current Seminoles juniors P.J. Williams and Ronald Darby being draft eligible.
McFadden is the second ESPN 300 prospect from Florida to commit to coach Jimbo Fisher in the past week after running back and ESPN 300 No. 42 prospect Jacques Patrick committed to the Seminoles on Monday.
McFadden's pledge gives the Seminoles six commitments among the top 15 players in the state of Florida. In-state commitments include No. 1-ranked athlete George Campbell and No. 1-ranked safety Derwin James Jr.
The Seminoles have 19 commitments and remain in the running for No. 1 Terry Beckner Jr., No. 2 Byron Cowart, No. 5 Josh Sweat, No. 8 Kendall Sheffield, No. 9 CeCe Jefferson, No. 58 Da'Vante Phillips and others.
Beckner Jr. announced on Thursday that Florida State will receive one of his five official visits. Sweat is scheduled to officially visit Tallahassee on Nov. 22.