He was best known for his roles as Norman Wilson in The Wire, Martin Querns in Oz, the game show announcer in Square One Television, and Freddy Hayes in House of Cards, the last earning him three consecutive Emmy Award nominations for Outstanding Guest Actor in a Drama Series, including a win in 2015.

He played the villain Dirty Dee in the cult comedy film Pootie Tang and had a regular role on the HBO series The Wire as Norman Wilson during the fourth and fifth seasons.

[14] He also worked with The Wire creator David Simon on the Emmy Award-winning miniseries The Corner; Cathey played a drug addict known as Scalio.

He narrated Aftermath: Population Zero, a National Geographic Channel special which imagines what Earth might be like if humanity no longer existed.

He also made a guest appearance on Law & Order: Criminal Intent in the episode "Anti-Thesis" as a college professor suspected of murder.

His portrayal of Hayes in the second, third, and fourth seasons of House of Cards earned three Emmy nominations and one win for Outstanding Guest Actor in a Drama Series.

One of Cathey's final TV roles was portraying James Lucas in the Netflix series Marvel's Luke Cage.