As a member of The Nolans, she first performed on television in 1974. She was a full-time member of the group from 1980 to 1994. The group was particularly successful in Japan, where they won the Tokyo Music Festival in 1981 and a Japanese Grammy Award in 1992. She was a member of the line-up that reformed for a successful tour of the UK and Ireland in 2009.
The Nolans made their television debut in 1974 on the show It's Cliff Richard. With the line-up featuring all six sisters and billed as The Nolan Sisters, they performed Stuck on You. That same year, they released their debut single But I Do, with Coleen singing lead vocals. Due to her age, Coleen would not become a full-time member of the group until 1980, when she was fifteen, although she does appear in the music video to their 1979 hit I'm In the Mood for Dancing, which reached number three in the UK singles chart. They also had UK top twenty hits with, Don't Make Waves (1980), Gotta Pull Myself Together (1980), Who's Gonna Rock You (1981), Attention to Me (1981), Chemistry (1981) and Don't Love Me Too Hard (1982). In 1981, they won the Tokyo Music Festival with the song Sexy Music. In 1991, the group won a 33rd Japan Record Awards Kikaku-shō (Prize for Planning) for Cover version of Japanese pops.
On 5 February 1974, Nolan made her first television appearance with her sisters when she was almost nine years old, as the Nolans appeared on the It's Cliff Richard! television series. On 14 January 1987, she appeared alongside her sisters Anne, Bernie and Maureen in the BBC sitcom Filthy Rich & Catflap.
In 2000, Nolan became a regular panellist on ITV's Loose Women. She remained with the series on and off for eleven years (taking a break to have and care for daughter Ciara).
Nolan made her last appearance as a panellist on Loose Women on 28 July 2011. On 7 October 2013, Nolan returned as a regular panellist. Since July 2015, Nolan has also been an occasional anchor of the show.
In April 2009, Nolan presented the programme, The Truth About... Eternal Youth about plastic surgery on ITV.
In 2010, Nolan presented The Secret Guide To Women's Health on Sky Real Lives.
In 2000, Nolan played the part of Janelle Cooper in the short comedy film, Rattler.
Beginning on 11 January 2009, Nolan took part in the fourth series of Dancing on Ice on ITV. Of her appearance on the show Nolan said, "I've never really skated. When I was 14, I used to go to Disco Beat in Blackpool with my friend. We'd skate round once, hanging on to each other, and spend the rest of the night posing, like 14-year-old girls do. I could only go forwards, I couldn't stop!" She was eliminated in week ten, finishing in fourth place.
Nolan co-hosted the spin-off show Dancing on Ice Friday with Ben Shephard on ITV.
On 27 February 2011, Nolan hosted Dancing on Ice, in place Holly Willoughby who fell ill.
On 15 August 2012, Nolan was announced as the eleventh celebrity to enter the Celebrity Big Brother house on Channel 5.
In 2013, Nolan was a resident agony aunt on the ITV chat show The Alan Titchmarsh Show, appearing on the show every Friday.
In 2015, Coleen took part in ITV's Give a Pet a Home series which worked alongside the RSPCA in Birmingham. The show began airing in April 2015, with Amanda Holden as host.
In 2017 Nolan participated in Celebrity Big Brother again. In the house she struck up a good friendship with Game of Thrones actor James Cosmo. On day 18 she was put up for eviction by Jamie O'Hara during a nominations twist in the superheroes shopping task. On day 19 it was revealed that Nolan received the most votes out of her, Chloe Ferry, Kim Woodburn and Jedward in a live flash vote. Also on day 19, she voted for Cosmo to gain internal immunity which he eventually won after the most housemates voted for him. On Day 32 (February 3rd), she was announced as the winner of Celebrity Big Brother 19.
On 4 March 2002, Nolan was a panellist on BBC panel game show Never Mind the Buzzcocks. On 25 May she appeared on An Audience with Brian Conley. Later in 2002, she took part in the first series of the reality television programme Celebrity Fit Club, which followed overweight celebrities as they tried to lose weight for charity.
On 7 January 2003, Nolan appeared in the documentary We Are Family that chronicled the success stories of various musical acts that were made up of family members. In 2002 and 2003, she was a panellist on the chat show The Wright Stuff on Five and guest hosted the show herself in 2013.
On 3 June 2005 Nolan took part in the first series of the ITV daytime programme, Have I Been Here Before? presented by Phillip Schofield, which offered celebrity guests the chance to see if they have lived before, through past life regression. Nolan was said to have been a "nervous 16-year old debutante".
In September 2006, Nolan returned to Celebrity Fit Club as part of the judging panel in the fourth series. On 6 October, she was a guest on The Sharon Osbourne Show and, ten days later, was a guest on the Irish chat show, broadcast and produced by RTÉ, The Podge and Rodge Show.
On 19 September, Nolan appeared on Al Murray's Happy Hour and on 27 September, she appeared with her family on the third series of All Star Family Fortunes competing against Barry McGuigan and his family. She has also made guest appearances on Alan Carr's Celebrity Ding Dong (31 October) and The Paul O'Grady Show (18 December), both on Channel 4.
On 13 September 2012 she was a guest panellist on an episode of Celebrity Juice on ITV2.
On 15 February 2013, Nolan stood in for Matthew Wright as host of The Wright Stuff on Channel 5.
Nolan has a weekly column in Best magazine.
In 2007, Nolan featured in television advertisements for the supermarket chain Iceland, along with her sister Bernie and former Loose Women colleague Kerry Katona. She appeared in further commercials for Iceland during the next couple of years.
Nolan was the new face of Park Christmas Savings and appeared in their television advertisements in December 2010.
In early 2008, she released a DVD, A Brand New You, produced with Rosemary Conley.
Nolan is the youngest of eight children and the only one born in England. She married Shane Richie in 1990, and they had two sons, Shane Nolan (born 2 December 1988) and Jake Roche (born 16 September 1992) together before splitting up in 1997 and divorcing in 1999. She gave birth to a daughter, Ciara, on 19 June 2001 and became engaged to her longtime boyfriend Ray Fensome (a musician who is from Leeds) when he proposed on her 40th birthday in 2005. They married in November 2007.
Nolan has undertaken charity work for the Alzheimer's Society, including cycling the River Nile in Egypt. Her late mother, Maureen, was a sufferer. In 2006 Nolan opened the first Alzheimer's Society information centre on the Fylde coast.
Nolan's mother died on 30 December 2007.
Nolan has gained media attention at times for controversial statements and opinions. In 2005, on Loose Women she claimed that if her 16-year-old son passed his exams then she would pay for him to go on a sex trip to Amsterdam and that she had given her fiancé Ray Fensome permission to have a one-night stand during the proposed trip. She was criticised by Shane Richie, who said he was "disgusted and appalled" by her comments about their son, and that he hoped and assumed "it was said in total jest. I can assure everyone that having passed his GCSEs fingers crossed Shane Jr will not be going to Amsterdam". English doctor and author Miriam Stoppard said of Nolan's comments, "the world's gone insane" and claimed that Nolan seemed to be shirking her responsibilities to deliver sex education.
However, Nolan defended her comments saying that she had told her son that she would pay for a long weekend for him anywhere in the world and that he had mentioned how he and his mates had "always wanted to go to Amsterdam to see the red light district. If he planned to go on a trip to Ibiza everybody would have thought that was fine, even though he would probably have unprotected sex with lots of girls." In the News of the World newspaper she said, "In an ideal world I'd never condone my son sleeping with hookers, but it's a fact of life that boys of his age have casual sex. So if I'm pushed, I'd rather he does it somewhere well-policed and where the girls have health checks than behind the wall of a club in Ibiza with absolutely no safeguards."
She added about her comments about Fensome, "In all honesty, I couldn't care less [if he does]. What bothers me more is the thought of Ray going into a bar, chatting up a really stunning girl, having sex with her, spending the night and waking up with her the next morning. I couldn't cope with that."
In January 2007, Nolan courted further controversy when, during a debate on Loose Women about gay adoption, she stated that gay people should not be allowed to adopt children, and said that "there's only so much I want to accept".
In May 2015, she sparked outrage from viewers by comparing gay rights with supporting ISIS and by saying that bakery owners should be permitted to discriminate against same-sex couples who wish to buy a wedding cake. Her comments were made on Loose Women after a Belfast bakery company was successfully sued for refusing to bake a cake in support of same-sex marriage. Following the show, viewers took to Twitter and called for ITV to fire Nolan for making the comments.