He played the role of Chris Pérez alongside Jennifer Lopez in the movie Selena, and portrayed U.S. Marine John Basilone, recipient of the Medal of Honor, in Tom Hanks and Steven Spielberg's The Pacific.

The writers, taking advantage of his boxing background, wrote a shirtless practice bout into an episode, which established his character's attractiveness to fellow detective Laura Ballard.

He is featured as one of the three leads in the HBO World War II mini-series The Pacific (released on March 14, 2010), portraying Marine John Basilone.

Seda appeared in Treme seasons 2-4 as Nelson Hidalgo, a politically connected land developer from Dallas who helps out with the relief efforts in post-Katrina New Orleans.

[13] In 2013, Seda starred alongside Sylvester Stallone, Christian Slater, and Jason Momoa in the Walter Hill-directed action thriller Bullet to the Head.

[15] On April 19, 2019, it was reported that NBC/Wolf Entertainment officials informed Seda that they would not be renewing his contract, which led to his leaving the series shortly after six seasons.

[16] In 2020, Seda was cast in the lead role of Dr. Benjamine Glass in the pilot of the NBC apocalyptic drama series La Brea, written by David Appelbaum,.