He is known for his roles as Manchester Black in Supergirl (2018–2019), Captain Roy Eris in Nightflyers (2018), and Cleveland "Book" Booker in Star Trek: Discovery (2020–2024).

[7] On TV he has appeared in many series including Doctor Who[5] and in major roles in Black Box, Beowulf: Return to the Shieldlands, Nightflyers, and Falling Water.

[8] Sean 'Mac' McAlister, a character from 2017 video game Need for Speed Payback, is voiced by and modeled after him.

Ajala has appeared as Keith in the BBC Radio 4 dramas Burned To Nothing (2011)[9] and Felix in The Price of Oil: Someone's Making A Killing In Nigeria both by Rex Obano.

[11] From 2020 to 2024, Ajala played the series regular role of Cleveland "Book" Booker in the third through fifth seasons of Star Trek: Discovery.