As the first British woman to be signed by the beauty brand since model Kate Moss in 1998, Cole could go on to feature in wider campaigns for the global cosmetics company, which normally starts its faces on one-year contracts.
Her work will start with a major TV ad campaign in October to promote a new range of hair products called Elvive Full Restore 5, which launch in the UK next month.
Gayle Tait, general manager of L'Oreal Paris, said: "Cheryl is a glamorous, stylish and talented young woman whose warmth and charm has captivated the nation and helped to establish her as an inspiration to women throughout the UK."
Cole's one-year contract with L'Oreal is said to be worth £500,000.
She said: "I have always loved the brand and have always wanted to say the iconic phrase 'because you're worth it' so to be given that opportunity is absolutely amazing.
"Every woman has the right to feel beautiful and L'Oreal Paris makes that aspiration achievable."
Cole replaced Sharon Osbourne as a judge on 'The X Factor' last year in the show's fifth series and recently travelled to the US to investigate media opportunities.
She was introduced to contacts stateside by 'X Factor' guru Simon Cowell, who is well known as a judge on 'American Idol'.
Other actresses and singers who have modelled for L'Oreal include Beyonce, Jane Fonda, Andie MacDowell and Jennifer Aniston.