He is the son of Barbara (née Colton), a homemaker, and Albert "Al" Gerstenfeld, a hearing aid salesman. He has two older brothers, Jeff and Paul.
He attended George Ellery Hale Middle School in Woodland Hills and graduated from El Camino Real High School in Woodland Hills.
He understudied Lane in the role of Oscar Madison, and substituted for him in January, 2006, during Mr. In 2006, Fox network announced they would pick up a new sitcom called 'Til Death starring Garrett in the lead role.
The plot revolves around a long married couple whose new next door neighbors are a pair of feisty newlyweds. He also appeared onstage on American Idol season six (2007) during judging on week 11, to which Ryan Seacrest said, "And the next person off American Idol is—Brad, you're out." In the fall of 2008, Garrett starred in, and was the executive producer for, an online reality show called Dating Brad Garrett.
He also appeared on Hollywood Squares including a memorable moment when he impersonated Bill Cosby during a question about Jell-o.
He then appeared in the short-lived summer comedy First Impressions (CBS, 1988), in which he was a divorced father who makes a living doing impressions, in a one-time spot as a bank loan officer on Roseanne (ABC), and The Pursuit of Happiness (NBC, 1995–96), in which he was the hero's gay best friend.
On the May 2, 1996 episode of the sitcom Seinfeld, called "The Bottle Deposit", Garrett played a deranged auto mechanic who steals Jerry Seinfeld's car.
He won the fifth season championship of Celebrity Poker Showdown, and played in the 2005, 20 World Series of Poker.
His appearance with Carson brought Garrett a lot of national attention, and soon he was appearing as an opening act for such headliners as Diana Ross and Liza Minnelli.
He also opened in Las Vegas for Frank Sinatra, David Copperfield, Smokey Robinson, Sammy Davis, Jr., the Beach Boys, the Righteous Brothers and Julio Iglesias.
Garrett has also made an appearance on The Fresh Prince of Bel-Air playing a hitman who attempts to kill Will Smith's character.
Garrett in May 2007 Garrett's distinctive deep voice has landed him prolific work as a voice actor, such as on Mighty Ducks: The Animated Series, 2 Stupid Dogs, The Spooktacular New Adventures of Casper, Project Geeker, Steven Spielberg Presents: Toonsylvania, A Bug's Life, Finding Nemo, Ratatouille, Asterix and the Vikings, Superman: The Animated Series, and Justice League Unlimited as Lobo.