He started his acting career in the late 1990s, appearing in a number of off-Broadway stage productions. Among his first film roles were Bad Company and Kissing Jessica Stein. His breakout role came in 2002's Barbershop, in which he plays reformed street thug Ricky Nash, a role that he reprised in the 2004 sequel, Barbershop 2: Back in Business.

In 2003, he played the role of Slap Jack in the second installment of the Fast and the Furious film series, 2 Fast 2 Furious. Later in 2004, Ealy appeared in Never Die Alone with DMX. He also appeared in Mariah Carey's music video for her hit single "Get Your Number" from her 2005 album The Emancipation of Mimi.

In 2005, Ealy co-starred in the Television film version of Their Eyes Were Watching God, produced by Oprah Winfrey and Quincy Jones, and starring Academy Award-winning actress Halle Berry.

The same year, he starred in the independent film Jellysmoke, directed by Mark Banning. He starred in the Showtime television series Sleeper Cell, the first season of which aired December 4-18, 2005, and the second season of which, Sleeper Cell: American Terror, aired December 10-17, 2006.

On December 14, 2006, Ealy was nominated for a Golden Globe Award for his role in Sleeper Cell: American Terror in the category Best Performance by an Actor in a Mini-Series or Motion Picture Made for Television. In December 2008 he was featured in the movie Seven Pounds alongside Will Smith as Ben Thomas. He also starred as the male lead in Beyonce's "Halo" music video, and as CIA Field Officer Marshall Vogel in the ABC television series FlashForward.

Ealy also appears in the limited-edition coffee table book (About Face) by celebrity photographer John Russo, published by Pixie Press Worldwide. He is currently working on independent writing projects. In 2009, Ealy performed in The People Speak, a documentary feature film that uses dramatic and musical performances of the letters, diaries, and speeches of everyday Americans, based on historian Howard Zinn's A People's History of the United States.