McGiffin was born in Islington and brought up in Maidstone, Kent, to British parents, John McGiffin and Heather Barham (d. 2003). She has two sisters and a brother. Her father walked out on the family when Carol was 4, leaving her mother to bring up the family on her own.
She started her broadcasting career in 1988 as co-host of the Chris Evans shows on GLR. Her style then and characterised today is based on comedic observation of men.
In 1995 McGiffin was a founding member of the Talk Radio UK team, co-presenting the popular weekday evening show The Rude Awakening with Moz Dee. When the show ended in September 1995 she became the station's music expert for around six months, hosting her own Friday evening review slot and appearing every week on Jonathan King's programme. In late 1996 she reappeared on Liberty Radio, co-hosting the breakfast show with Richard Skinner for six months. In 1997 and 1998 she united with Paul Ross and Nick Abbot in varying time slots.
In 1999 she joined London radio station LBC teaming up again with Abbot, who left the station after six months. McGiffin continued to host the show on her own with producer/sidekicks, including Marcus Railton and Jonathan Sanchez until 30 September 2000. She co-hosted phone-in shows on BBC London Live. In 2002, she occasionally teamed up with Abbot on Real Radio.
She joined Live Talk in 2000, and was a regular from the start to finish in 2001. She then returned to the rebranded version of Live Talk, Loose Women in 2003, where she continued until her departure in 2013. She holds the current record for the most appearances (in 1,172 episodes).
Between February and July 2006 she was the southern presenter of the Local Radio Company's night-time talk show North South Divided. Mike Elliott was her northern counterpart. In August 2006 McGiffin returned to LBC 97.3 presenting a Sunday morning show. McGiffin's weekly views on the world and travel advice in her Travel Clinic ended on 10 February 2008, when she left the station. Throughout the summer of 2012, she regularly reviewed the daily newspapers on This Morning. In August 2013, she entered the Celebrity Big Brother house to compete in the twelfth series, where she finished in fourth place.Loose Women (2003–2013) – Regular Panellist
Daily Cooks Challenge
Who Wants to Be a Millionaire? – Contestant (2007)
Tonight with Trevor McDonald
Ant and Dec's Saturday Night Takeaway
The Paul O'Grady Show – Guest
The Jack Docherty Show
8 Out of 10 Cats – Panellist
Friday Night with Jonathan Ross
Celebrity Juice – Panellist
The Justin Lee Collins Show
The Wright Stuff (2014–2017)
Pointless – Contestant
This Morning (2012, 2016) – Newspaper Reviewer
Celebrity Big Brother (Summer 2013) – Housemate
Celebrity Big Brother's Bit on the Side (Summer 2013) – Guest
Celebrity Big Brother's Bit on the Psych (Winter 2014) – Panellist
McGiffin is a survivor of the 2004 Indian Ocean earthquake. For several years, she has returned to Maidstone to join members of her family and take part in Race for Life to raise money for the charity Cancer Research UK, she does this in memory of her mother. McGiffin was also a smoker but quit some years ago.
She resides in Hampstead, North London. She married presenter Chris Evans in 1991. They separated in 1993 and divorced in 1998. She has been engaged to Mark Cassidy since 2008.
In February 2015, McGiffin announced that she was battling breast cancer that she had been diagnosed with a year earlier. She has undergone radiotherapy and chemotherapy treatments as well as having a mastectomy.
In 2010, McGiffin released her autobiography, Oh, Carol!.