Campbell was born in Streatham, South London. She is of mostly Afro-Jamaican heritage, though her father is also partially of Jamaican-Chinese descent. Campbell attended the London Academy For Performing Arts.

A graduate of the Italia Conti Academy stage school, Campbell's first appearance to a wider public was in February 1978 when she was cast as a pupil to appear in a music video with Jamaican reggae superstar Bob Marley for his song Is This Love?.

On graduating from Italia Conti, her looks created her an income and she switched to become a fulltime model, creating a high profile career and creating two spin-off companies: NC Connect and a self-named line of perfumes.

Her charity work mainly focuses on the children and people of Africa, including working with Nelson Mandela, since 1997. In 2005 she helped to create and participate in 'Fashion Relief' for Hurricane Katrina victims, raising over a million dollars.

Aged 15 and while still a student of the Italia Conti Stage School, Campbell was spotted by Beth Boldt, former head of Synchro models agency, window-shopping in Covent Garden. In April 1986, she made the cover of Elle, when another black model had to cancel the job. By August 1988, she had graced the cover of French Vogue as the publication's first black cover girl and completed campaigns for Ralph Lauren and Francois Nars.

Her modelling career started as a catwalk model, but she was quickly picked up for various high profile advert campaigns for Lee Jeans and Olympus Corporation, which broke her in to America. The highpoint of her career was in the early 90's when she was part of the two major supermodelling powerhouses, the Big Six and the Trinity, (with Linda Evangelista and Christy Turlington).

She has walked for many fashion designers, including Gianni Versace and Valentino. Campbell famously tumbled over on the catwalk at Vivienne Westwood's Anglomania fashion show in 1994. Campbell was the first black model to appear on the cover of Time magazine and French and British Vogue. She has also appeared on the covers of Harper's Bazaar and ELLE magazine.

She posed nude for Playboy magazine and for a series of lesbian-erotic photos with Madonna in the latter's book Sex.

Campbell has appeared in music videos for artists such as Michael Jackson, Jay-Z, Macy Gray, Prince, Usher and also Madonna's music video, "Erotica", with Ingrid Casares on 12 October 1992. She had previously appeared in George Michael's music video, "Freedom '90", where she lip-synched to his song along with other models.

Campbell has also tried her hand at singing. Her album Baby Woman sold over 1 million copies worldwide (mostly in Japan), and she was featured on Vanilla Ice's single "Cool as Ice." In 1995, her collaboration with Toshinobu Kubota, "La La La Love Song", became a #1 hit in Japan, with the single selling approx. 1,856,000 copies. That same year she lended her vocals to music legend Quincy Jones' album "Q's Juke Joint"

Campbell "co-authored" the best-selling novel Swan in 1996, and followed it up with a photography book titled Naomi. But when questioned about her use of a ghost writer for "Swan", Campbell admitted that she wrote almost none of the book: "I just did not have time to sit down and write a book"

Campbell has dated many famous personalities. She was rumored to have a brief relationship with boxer Mike Tyson in the late 1980s, and also U2's bassist Adam Clayton. In the 1990s Campbell dated actor Robert de Niro, dancer Joaquin Cortes and with F1 boss Flavio Briatore. In late 2004 she had a high profile relationship with Usher, although by 2005 their relationship appeared to be over. In addition, she has been romantically linked to musician Eric Clapton, actor Sylvester Stallone, Prince Albert, Robert Goode, Matteo Marzotti, and actor Leonardo DiCaprio, among others.

In February 2001 pictures were published in the Daily Mirror newspaper showing Campbell leaving a Narcotics Anonymous meeting in London. In March of 2002 Campbell sued the paper citing a breach of confidentiality, as she was receiving treatment for drug addiction at the time. The Mirror claimed that the pictures were in the public interest as Campbell had denied having a drug problem publicly and had, up to that point, not been known or proved to be a drug addict. The High Court ruled in Campbell's favour and the Mirror was ordered to pay £3,500 in damages (although legal costs were thought to be around £500,000.) In October of 2002, the Mirror won an Appeal Court ruling that the photographs were indeed in the public interest. Campbell was ordered to pay the costs of the Mirror's legal fees, a cost of around £350,000. However, in May of 2004, the Law Lords overturned the Appeal Court ruling by a 3 to 2 majority, which reinstated the High Court's original decision, and Campbell was rewarded £3,500 and the £350,000 legal costs. The Mirror's legal cost is thought to be over £1,000,000. The case is also thought to be a landmark in the rights of celebrities to privacy.

Campbell is purported to have had feuds with several celebrities, the most publicized of which is with fellow model Tyra Banks. The two finally made up in 2005 on an episode of Banks' syndicated talk show The Tyra Banks Show. At the end of the 2005 Victoria's Secret Fashion Show, Banks and other models exited the runway and Banks explained her emotions of the event being her last runway show as a fashion model; and as she was talking Campbell came to hug Banks and kiss her on the cheek.

Campbell also had a rift with former Spice Girl Victoria Beckham, who publicly branded the model as a "massive cow" and a "bitch" in 2000. They have since been photographed holding hands at a fashion show so a truce appears to have taken place.

Campbell has been accused of committing acts of violence and verbal abuse against some of her employees and associates. Documented accusations include:

In 2000, she pleaded guilty in a Toronto court to a 1998 assault on Georgina Galanis, her then assistant; Campbell had assaulted Galanis with a telephone in a hotel room and threatened to throw her out of a moving car. Under an agreement with the prosecution her record was cleared in exchange for her expressing remorse; Campbell also paid Galanis an undisclosed amount of money and agreed to attend anger management classes.

March 2005, the model was said to have slapped assistant Amanda Brack and beaten her around the head with a Blackberry handheld personal organiser. The star's spokesman Rob Shuter denied the incident ever took place. In July 2006, Brack began proceedings against Campbell, claiming the supermodel abused her verbally and physically on three continents. Brack accused Campbell of assault, battery, false imprisonment and infliction of emotional distress in incidents that started a month after she began working for her in February 2005.

Italian actress Yvonne Scio has claimed the model left her "covered in blood" after a spat at a Rome hotel. Yvonne claimed: "She punched me in the face. She was like Mike Tyson."