Phillips was born in Greenwich, Connecticut, and is the daughter of John Phillips of The Mamas and the Papas and his then-wife Geneviève Waïte, a South African model. She also is the half-sibling of Mackenzie Phillips, Jeffrey Phillips and Chynna Phillips. Her older brother is Tamerlane Phillips. The name "Bijou", which is French for "jewel," was taken from the song "My Petit Bijou" by Lambert, Hendricks and Ross.

Phillips had a tumultuous childhood, and began modelling at an early age. She appeared on the cover of Interview when she was 13 and soon became the youngest Vogue cover model when she appeared on the Italian edition. By the age of 15 she was leading an adult life, living in her own apartment in Manhattan and subsisting on her modeling salary. During this time, she became a "wild child" of the New York City party scene, frequenting nightclubs such as Limelight and Spy Bar. Her half-sister, Mackenzie, was sometimes seen accompanying Bijou to various fashion shows, playing the role of surrogate parent.

At the age of 17, she was granted a record deal with Almos Records and ended her modelling career; her debut album was titled I'd Rather Eat Glass, a sentiment that expressed her feelings about her former profession. Around the same time as the release of her album in 1999, she began acting in independent films. The following year, she posed nude for Playboy and appeared on the cover of the April, 2000 issue. As of 2005, Phillips continues to act while she records tracks for her second album.