He voiced Endrance in .Hack//G.U. vol 1//Rebirth, .Hack//G.U. vol 2//Reminiscence, and .Hack//G.U. vol 3//Redemption.
He voiced Cain Highwind in the video game Final Fantasy IV DS.
He voiced Lieutenant Colonel Detlef Fleisher in the video game Ace Combat Zero: The Belkan War.
He voiced Kotetsu Hagane in the video game Naruto: Ultimate Ninja.
He was the ADR script writer for the Blue Dragon video game.
He voiced Gensou in Zatch Bell however he is uncredited.
He was the ADR script writer for several Naruto video games such as Naruto: Clash of Ninja Revolution, Naruto: Rise of a Ninja and Naruto: Uzumaki Chronicles 2
He voiced Sanctus in the video game Devil May Cry 4.
He voiced Isaac in the video game Castlevania: Curse of Darkness.
He voiced Nadara Roga in Naruto The Movie: Ninja Clash in the Land of Snow
He voiced Akihiko Sanada in the video game Shin Megami Tensei: Persona 3.
He tends to voice characters that insane or complete evil geniuses. Examples of this include his roles as Gaara, Lezard Valeth, and Dist.
His best known role that he gets the most praise for is Gaara of the Desert on Naruto.
He was the English voice director for the video game Ace Combat 6: Fires of Liberation.
Liam O'Brien has short brown hair and brown eyes.
He was nominated for "Best Voice Actor in an Anime Comedy" by the American Anime Awards.
Liam was a writer in the English adaptation of Naruto the Movie: Ninja Clash in the Land of Snow.
He plays Frank Lubey in All My Sons, a play by Arthur Miller.
Liam O'Brien was part of the 100 voice actors who were interviewed about their careers for Adventures in Voice Acting.
O'Brien has a child with his wife, Amy Kincaid. He's a boy and his name is Owen Kincaid O'Brien.
O'Brien tends to work in Fantasy, Anime, comic-based, and Action/Adventure genres. He tends to play unusual or evil roles.
In Final Fantasy VII Advent Children Liam O'Brien provides the voice for Red XIII.
His ethnicity is Irish-American.
He is married to fellow voice actress Amy Kincaid.