Getty was born as Paul Balthazar Getty in Tarzana, California and raised in San Francisco before being sent to private school in Britain, where he was enrolled at Gordonstoun School, an elite boarding school that has educated three generations of the British Royal Family. His great-grandfather is the late Jean Paul Getty, founder of the Getty Oil Company, and at one time one of the richest men in the world. His father is John Paul Getty III, and his mother, Gisela Martine Getty (née Schmidt), is a professional photographer and documentary filmmaker. His parents are now divorced. Getty has a sister, Anna.

Getty entered the movie business in 1987 when he auditioned for the lead role in the movie Lord of the Flies after being spotted by a talent scout in his art class at school. During the course of the 1990s and early 2000s, he has appeared in films such as Young Guns II, Natural Born Killers, Judge Dredd, White Squall, Lost Highway, Big City Blues, The Center of the World, Deuces Wild, Ladder 49, Feast and the television series Traffic.

Getty guest-starred on the television series Charmed as Richard Montana, a male witch who at one point was romantically linked with Paige Matthews. He appeared in the fifth season of the hit show Alias as Agent Thomas Grace. He currently stars, alongside Alias costar Ron Rifkin, in the ABC prime time drama Brothers & Sisters, which first aired in September 2006. Getty plays the role of Thomas "Tommy" Walker, one of the five Walker siblings.

In late 2008, it was reported that Getty's contract as a full-time series regular will not be renewed due, in part, to budgetary and storyline considerations, though Getty may return in a reduced capacity. On the Season 4 premiere, Balthazar Getty was still listed in the principal cast, but he did not appear. Getty finally made his highly-anticipated return to the series in the sixth episode of Season 4. Although he no longer appears in every episode, he continues to make sporadic appearances on the show.

In 2000, Getty married fashion designer Rosetta Millington. They have four children: Cassius Paul, Grace, Violet, and June Catherine.

In July 2008, Getty was photographed kissing a topless Sienna Miller aboard a boat and on a hotel balcony in Italy. Getty and Miller had reportedly been dating since May 2008, shortly after his wife Rosetta gave birth to the couple's fourth child. On July 21, 2008, Getty released a statement confirming that he and his wife had separated, although to date no divorce has been filed. Getty and Miller have since separated, as well.