The actor, 79, dropped his memoir, You Never Know, on May 7, reliving the most significant events of his life and career, including shooting to fame in the '80s as a TV star, his marriages, and his desire to keep acting.
Take a look back on the star's screen career, from his early roles in the '70s to his current tenure as one of TV's beloved patriarchs, and how much he's transformed…
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Screen debut
After brief appearances in game shows and TV commercials, Tom started making minor appearances in series Bracken's World, Wide World Mystery, and The Young and the Restless.
Tom is pictured here in an episode of Wide World Mystery in 1973 titled "Shadow of Fear."
In the late '70s and early '80s, inspired by his own love for the outdoors, the actor began taking on more roles in Westerns like The Sacketts (pictured here) and Concrete Cowboys.
He continued that trend into the '90s as well, having established himself at that point as a rugged but charming TV mainstay.
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Magnum P.I. and shot to stardom
In 1980, Tom skyrocketed to fame when he took on the role of Thomas Magnum in Magnum P.I. (at the cost of Indiana Jones, no less), playing the role for eight years.
He became well known as an action star thanks to the series, but his easy charm and good looks also made him a sex symbol of the '80s, despite not being interested in that title himself.
As his profile grew, so did his roles in movies, taking his comedic chops and quick wits to the silver screen with hits like Quigley Down Under (1990) and Mr. Baseball (1992).
His best remembered movie role is 1987's Three Men and a Baby, a commercial success that launched an entire franchise.
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The dignified '90s
Tom moved into the '90s on the back of the success of Three Men and Magnum and found success specifically by embracing his age and stature.
That was best exemplified in his recurring turn in Friends, playing Monica Geller's older boyfriend Dr. Richard Burke, winning over a whole new audience and earning an Emmy nomination for it.
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Viva Las Vegas!
The dad-of-two's career slightly stagnated in the aughts, but he found success once again in the TV space with made-for-TV movies and recurring roles.
In 2007, he joined the cast of Las Vegas for its fifth and final season, his first regular TV role since Magnum.
His longest TV tenure began in 2010 when he signed on to play the patriarch of a family of NYPD officers, Frank Reagan, in the CBS procedural drama, which has been a ratings hit since its debut.