Olusanmokun was born in Lagos, Nigeria, in 1984. He moved to the United States to attend college, where he studied theater at the University of California, Los Angeles. After graduating, he began his acting career in New York City.

Olusanmokun's first major film role was in the 2017 episode of Black Mirror titled "Black Museum." He then went on to appear in the films Too Old to Die Young and Dune. In 2022, he began starring in the Paramount original series Star Trek: Strange New Worlds as Dr. Joseph M'Benga.