Before becoming a reality star, McLean modelled for Page 3 of The Sun between September 1999 and July 2004, and the Daily Star from 2000 until 2006. McLean came fourth in The Sun poll for the "Best Page 3 Girl Of All Time", beating Samantha Fox, Jo Hicks, Leilani Dowding, and Jordan, whose rivalry with McLean has been widely publicised.
During her time as a glamour model, McLean often featured on tabloid showbiz gossip pages and latterly as a guest on television shows including The Weakest Link (Page 3 special), Richard & Judy, The Big Breakfast, Test The Nation (WAGs Special) and The Sexiest Girls In Britain.
McLean retired from modelling in 2006 after giving birth. She decided to return to modelling, TV work, and acting in early 2008, after being asked to feature as a main star in the Channel Five TV documentary Help! I've Got a High Maintenance Wife. Since then, she starred in the TV show WAGS' World… With Nicola McLean on Wedding TV and Channel Five's Generation Sex. She returned to glamour modelling assignments in February 2008 with the Daily Star, and she has also appeared on more lads' mags covers. McLean was a contestant in the November 2008 edition of ITV reality TV show I'm A Celebrity, Get Me Out Of Here!. She clashed with fellow camp mate David Van Day during the series. McLean become the seventh celebrity to be eliminated and finished in sixth place on Day 18.
On 22 November 2008, McLean was chosen by Ultimo to model their range of D-G cup bras.
On 5 January 2012, McLean became a housemate on Channel 5's Celebrity Big Brother. She clashed with cast member Denise Welch in a now infamous row dubbed Pantsgate by the press and viewers and controversially shredded her fellow housemates' letters from home in order to gain her own, shouting "Shred Shred Shred!" as she did so. She was nominated on Day 7 of the series, but survived this eviction on Day 9. She was nominated again on Day 14, but survived this eviction on Day 16. McLean was the sixth housemate to be evicted, on Day 21 of the series, finishing in seventh place overall.
After her popular and controversial stint in Celebrity Big Brother, McLean become a regular fixture on the side show Big Brother's Bit on the Side and in one episode dated 18 September 2015, had a significant row with reality television star Farrah Abraham.
McLean entered the Celebrity Big Brother house for the second time in January 2017 as an All Star housemate. In the house she repeatedly clashed with Kim Woodburn and Jedward. She was nominated for eviction on Day 20 of the series, but survived this eviction on Day 22. On Day 25, she was nominated for eviction but survived this eviction once again on Day 27. On Day 29, after surviving the final public vote of the series, McLean become one of the show's finalists. During the final on Day 32, McLean finished in fifth place. She returned for Big Brother 18 as a special guest during a shopping task along with fellow ex-celebrity housemates Marnie Simpson and Gemma Collins. The trio stayed for 3 days before departing during a live show.
McLean is a supporter of PETA. In May 2009, she was spotted at a protest in London holding a sign that read "Unhappy Birthday Selfridges! Drop Cruel Foie Gras".
McLean was born in London to Scottish parents and has one sister. She married footballer Tom Williams on 13 June 2009. The couple have two sons, Rocky and Striker Williams.