[2][3] Onwuasor competed for a roster spot as a backup inside linebacker and special teams player against Zach Orr, Brennen Beyer, and Kavell Conner.

[9] Upon being added to the active roster, head coach John Harbaugh named Onwuasor the fifth inside linebacker on the Ravens' depth chart.

[10] On October 16, 2016, Onwuasor made his professional regular season debut and recorded one solo tackle as the Ravens lost 27–23 at the New York Giants in Week 6.

On January 1, 2017, Onwuasor earned his first career start after Orr was placed on injured reserve due to a neck injury he sustained the previous week.

[16] Head coach John Harbaugh named Onwuasor a backup inside linebacker, behind Mosley and Correa, to begin the regular season.

[3] Onwuasor entered training camp slated as a starting inside linebacker, but received competition from Albert McClellan, Bam Bradley, and Correa.

Onwuasor intercepted a pass by Broncos' quarterback Case Keenum, that was originally intended for tight end Jeff Heuerman, and returned it for an 89-yard touchdown before it was called back for a penalty in the fourth quarter.

[27] In week 9 against the New England Patriots, Onwuasor recorded a team high 8 tackles, sacked Tom Brady once, and forced a fumble on wide receiver Julian Edelman that teammate Marlon Humphrey returned for a 70 yard touchdown in the 37–20 win.