The series, which stars Jeff Daniels, Dev Patel, Emily Mortimer and Olivia Munn, focuses on a team working on a broadcast news programme.
The Expendables star Crews will play Lonny, the bodyguard of news anchor Will McAvoy (Daniels), according to Deadline.
Crews currently stars in TBS sitcom Are We There Yet? and will next be seen in action sequel The Expendables 2.
Other stars confirmed for The Newsroom include Alison Pill, John Gallagher Jr, Thomas Sadoski and Sam Waterston.
The series will premiere on HBO later this year.
> Jane Fonda joins Aaron Sorkin's HBO newsroom drama
Watch a trailer for HBO's 2012 schedule - including clips from The Newsroom - below: