On the football field, Reagor produced back to back 1,000-yard receiving seasons for Waxahachie head coach and former NFL quarterback Jon Kitna and was selected to play in the 2017 Under Armour All-America Game. His track & field career culminated with a gold medal in the long jump at the 2017 Texas High School state meet.

Reagor enrolled at Texas Christian University in Fort Worth, Texas in the summer of 2017 and made his collegiate debut in the Horned Frogs’ season opener against Jackson State with two receptions in TCU’s 63-0 victory. He scored his first collegiate touchdown two weeks later when he caught a Hail Mary pass from quarterback Kenny Hill on the last play of the first half in a victory over SMU. He scored touchdowns in each of the last four games of the season, which included TCU’s first-ever appearance in the Big 12 Championship Game and a win in the 2017 Alamo Bowl over Stanford. For his efforts, he was named Co-Big 12 Offensive Freshman of the Year.

Prior to his sophomore season, Reagor switched to jersey number 1 from the 18 he’d worn in 2017. That fall, he became the Frogs’ go-to receiver in a season in which they used three different starting quarterbacks, becoming the first TCU receiver to top 1,000 yards since Josh Doctson. He had a streak of 7 straight games with a receiving touchdown, which included a win against Oklahoma State in which he also recorded his first career 100-yard rushing game. After the season, he was named 2nd-team All-Big 12. In his 2019 season, he had 43 catches for 611 yards. Reagor declared for the 2020 NFL Draft after this season, forgoing his final year of eligibility.

Reagor was selected by the Philadelphia Eagles in the first round with the 21st overall pick in the 2020 NFL Draft, becoming the highest-drafted wide receiver to come from TCU since former All-American Josh Doctson in 2016. On July 20, 2020, Reagor signed a 4-year $13.3 million contract with the team, with a fifth-year team option. Reagor sustained a shoulder injury in training camp but recovered enough to play in Week 1.

On September 13, 2020, Reagor made his NFL debut against the Washington Football Team, finishing with one reception for 55 yards in the 17–27 loss. He was placed on injured reserve on September 30, 2020, after suffering a ligament tear in his thumb. He was activated on October 31, 2020. In Week 8 against the Dallas Cowboys on Sunday Night Football, Reagor recorded his first career touchdown reception during the 23–9 win.