Ramsey started all 14 games for the Florida State Seminoles as a true freshman in 2013. He was the first true freshman to start a game at cornerback for the Seminoles since Deion Sanders in 1985. Ramsey wore jersey #13 during his freshman year, where he won a national championship, and then switched to jersey #8 for his Sophomore and Junior year. Also, Ramsey chose jersey #17 for kick returns during his junior year, a number that had been retired in honor of former superstar Charlie Ward, who granted Ramsey permission to wear the number. He finished the year with 49 tackles, one interception, and one sack. He also competed on the Florida State Track & Field team, placing third at the 2014 ACC Indoor Championship in the long jump (7. 46 m). As a sophomore, Ramsey played 14 games with 2 interceptions, 12 passes defended, 3 forced fumbles, and 2 sacks on 80 tackles. As a junior, he played 13 games with 1 sack, 9 passes defended, and 1 fumble recovery on 52 tackles. On September 18, against Boston College, he recorded a 36-yard fumble return for a touchdown in the 14–0 victory. After his junior year, he announced his intention to forego his senior season and enter the 2016 NFL Draft.