Alaimo was born in Milwaukee, Wisconsin. He has a son from his first marriage, Michael Antony Alaimo (born 1971), who is a Writer, story Editor and Producer known for The Closer, Major Crimes, Invasion and Traveler. Alaimo has a daughter from his second marriage, Ariel Rose (born 1989), who is an Artist and Stylist.
He played several characters in Star Trek: The Next Generation, starting in the first season, including the first Romulan on the series, Commander Tebok, and the first Cardassian, Gul Macet, in the 1991 episode, "The Wounded," of that series. He also played a poker player who speaks French to Data in the episode "Time's Arrow". In 1993, Alaimo began playing Gul Dukat in Star Trek: Deep Space Nine. Gul Dukat was a recurring character, who appeared in 37 episodes of that series, and is his best-known character. He also appeared in a season two episode of 21 Jump Street.
Alaimo also featured in the 2006 video game Call of Juarez, and its 2009 prequel Call of Juarez: Bound in Blood, both times as the voice of the gunslinging Ray McCall. In 2010 he voiced The Dean in the Family Guy episode "The Splendid Source".
