Campbell's first public appearance came aged 7 in February 1978 when she was cast as a pupil to appear in a music video for Bob Marley's song Is This Love?. In 1982, she appeared in another music video, this time as a tap dancer for Culture Club's I'll Tumble 4 Ya.

At age 15 and while still a student at the Italia Conti Academy, Campbell was spotted by Beth Boldt, a former Ford model and head of the Synchro model agency, while window-shopping in Covent Garden. Campbell soon opted to become a fulltime model, signing with Elite Model Management. Although Campbell started her career as a catwalk model, she was quickly hired for various high-profile advertising campaigns, including Lee Jeans and Olympus Corporation, which introduced her to the American market. Campbell also completed campaigns for Ralph Lauren and François Nars. At age 15 in April 1986, Campbell appeared on the cover of Elle, replacing a model who had canceled out of the appearance.

In August 1988, she appe