[2] He is known for his roles as Clemson Murn / Ik Nobe Lok in the first season HBO Max show Peacemaker, as The High Evolutionary in the Marvel Cinematic Universe (MCU) film Guardians of the Galaxy Vol.

In 2006, he replaced David Oyelowo in the title role of the Henry VI trilogy in the revival of the This England: The Histories project.

[8] In 2013, Iwuji played Enobarbus in the Caribbean-themed Antony and Cleopatra directed by Tarell Alvin McCraney that was a joint production between the RSC and The Public Theater in New York.

In 2016, he played Hamlet for The Public's Mobile Unit, and he described his portrayal of the role as "this ugly, relentless beast that’s about to be unleashed.

"[9] In 2018, he starred as Othello at the Delacorte Theater for Shakespeare in the Park opposite Corey Stoll as Iago,[10] and as Blanke in The Low Road at the Public.

He performed at the Royal National Theatre in Welcome to Thebes in 2010, the Old Vic in a 2011 Richard III,[11] in 2014 off-Broadway in Tamburlaine for which theater critic Ben Brantley called him "a standout,"[12] and in 2016–17 with director Ivo van Hove in both Obsession and Hedda Gabler.

Iwuji appeared on a number of shows, including "The Impossible Astronaut", the first episode of Series 6 of Doctor Who (2011).