Stacy Ferguson was born in Whittier, California to parents Pat Ferguson and Terri Gore. She is of Irish and Scottish descent.

As a child actress, she appeared on the television program Kids Incorporated for several years with Renee Sands, who herself would become another member of Wild Orchid. Her well-scrubbed image on that show presents quite a contrast with the ghetto-funk image she has more recently begun to cultivate. Ferguson was the voice of Sally Brown in two Charlie Brown specials: It's Flashbeagle, Charlie Brown (1984), Snoopy's Getting Married, Charlie Brown (1985) and also voiced Sally in the 1985 version of "The Charlie Brown and Snoopy Show". She has one sister, Dana Ferguson, who is an actress. Later, Ferguson was a member of the female trio Wild Orchid which she fronted with fellow Kids Incorporated star Renee Sandstrom and Stefanie Ridel. Wild Orchid released two albums, but after completing a third album, their record label declined to release it. This prompted an emotional crisis, and Stacy sought therapy. She left the group shortly thereafter.

Her disappointment with Wild Orchid led to an addiction to ecstacy and crystal meth. She told a Glasgow paper: "I started doing Ecstasy. Then I got addicted to crystal methamphetamine. My weight dropped to 90 lb so I lied to my friends and said I was bulimic. Finally, I started going crazy."

On July 2003, she had a guest role on the Rocket Power special, Reggie's Big Beach Break, on Nickelodeon, voicing a fictitious pop music star named Shaffika.

In 2003, Ferguson took over the lead female vocal duties for the band, The Black Eyed Peas. Ferguson replaced background singer Kim Hill, who left the group in 2000. Ferguson recorded five songs with the group before she was invited to join them permanently. Ferguson's addition to the band, which had been formed years earlier, sent the group on a whirlwind of success. She appeared on the cover of FHM in January 2005. In 2006, Ferguson returned to acting, appearing in the movie, Poseidon. She is also featured as No. 36 on Maxim's Hot 100 list for 2006. After two hit BEP albums, Ferguson has turned her sights on a solo career. Her first album due in September 2006, is entitled, The Dutchess, a take on Sarah Ferguson's, The Duchess of York royal title, and the common 'Ferguson' surname. The solo deal however, does not mean the demise of the Black Eyed Peas. Ferguson is intending staying with the group, and alternating between the two duties. Music on The Dutchess is expected to be reminiscent of the Black Eyed Peas sound, most likely due to fellow BEP member, Will.i.am, featured on production duties. Ferguson worked with an array of talent, and the lyrics will focus on Fergie's own brand of style and delivery.