In the CFL Scouting Bureau's Final Rankings, Onyeka was named the 10th best player available in the 2018 CFL Draft.[3] In alignment with his ranking, he was selected with the 10th overall pick in the draft by the Edmonton Eskimos and signed with the team on May 16, 2018.[4] He made the team's roster following training camp and played in the team's season opening game on June 14, 2018, against the Winnipeg Blue Bombers. In his rookie year, he played in nine games where he made two defensive tackles.[5]
In 2019, Onyeka played in all 18 regular season games where he recorded three defensive tackles and 13 special teams tackles.[5] He also played in his first two post-season games, against the Montreal Alouettes in the Semi-Final and then the Hamilton Tiger-Cats in the Division Final, where he posted three defensive tackles and one special teams tackle over the two games.[5] He did not play in 2020 due to the cancellation of the 2020 CFL season and he became a free agent on February 9, 2021.[6]
Saskatchewan Roughriders
On the first day of free agency, on February 9, 2021, Onyeka signed with the Saskatchewan Roughriders.[7] He made a career-high eight defensive tackles against the Winnipeg Blue Bombers on September 11, 2021, in the Banjo Bowl.[5] On February 15, 2023, Onyeka re-signed with the Roughriders.[8]