Izzo grew up in Vernon Township, New Jersey and attended Pope John XXIII Regional High School in Sparta, New Jersey. He along with his parents felt that playing at Pope John would increase chances for exposure even though he would be switching positions. Initially, he had drawn little interest from NCAA Division I football programs, until Virginia Tech expressed interest and 20 other schools followed thereafter before he graduated in 2014. Along with playing football, he also played basketball. As a senior, he tallied 766 receiving yards and seven touchdowns. Izzo committed to play college football for the Florida State Seminoles on September 23, 2013.
As a redshirt freshman in 2015, Izzo played in all 13 of Florida State's games, catching 14 passes for 210 yards and two touchdowns. He also rushed for 146 yards and one touchdowns on 12 attempts.
In 2016, Izzo once again played in all 13 games, catching 19 passes for 227 yards, tallying one touchdown.
Prior to the 2017 season, Izzo was named to the John Mackey Award watch list. As a redshirt junior, he played and started in all 13 games for Florida State, having 19 receptions for 306 yards and three touchdowns.
His most notable moment that season came on Veterans Day against Clemson. With the ball on the Seminoles' own 40-yard line, quarterback James Blackman took the snap, handed the ball off to his running back, who pitched it to a wide receiver, who pitched it back to Blackman. Blackman found tight end Ryan Izzo wide open downfield, then Izzo dodged one defender and rumbled his way to the end zone for a 60-yard touchdown.