The Frisco, Texas native signed with Iowa State as a member of the class of 2016. Iowa State was his choice over other programs, including the ones from Indiana, Iowa Kansas, Nevada, Nevada, and Northwestern. In his first season with the program, Nwangwu was named a First-Team Kick returner of the Year by the All-American Freshman team by Pro Football Focus. The running back wasn't able to perform in 2017 due to the Achilles ligament torn in the spring after his freshman season. He bounced back in 2018 and was a Second-Team All-Big 12 selection as a kick returner for the coaches. The role of Nwangwu was expanded in 2019 when he became a major reserve running back . He was also the team's primary kick returner.

The Iowa State running back was the all-time record holder in kick return average. He averaged 26.8 yards per return over his career. He fielded at least 92 kickoffs throughout four seasons. In all, he ended his Iowa State career with 744 rushing yards on 143 attempts (5.2 yards per run) which included four touchdowns.