She and her books have won numerous awards, including the Irish Book Award for Popular Fiction for The Year I Met You.She has published several novels and contributed a number of short stories to various anthologies. Ahern also created and produced the ABC comedy Samantha Who? starring Christina Applegate.
She is a face of Littlewoods Ireland.
Ahern is the daughter of the former Taoiseach of Ireland, Bertie Ahern. Her older sister, Georgina Ahern, is married to Nicky Byrne of Irish pop group Westlife. In 2000, Cecelia Ahern was part of the Irish pop group Shimma, who finished third in the Irish national final for the Eurovision Song Contest.
Before starting her writing and producing career, she obtained a degree in Journalism and Media Communications from Griffith College Dublin, but withdrew from a Master's degree course to pursue her writing career.
On 14 December 2009, it was announced that Cecelia had given birth to her first child with husband David Keoghan, a girl named Robin. One of her spokeswomen confirmed in March 2012 that she was pregnant with a second child. Cecelia gave birth to her second child a boy named Sonny on 23 July 2012. They currently live in Malahide in North County Dublin.
In 2002, when Cecelia Ahern was twenty-one, she wrote her first novel, PS, I Love You. Published in 2004, it was the number 1 bestseller in Ireland (for 19 weeks), the United Kingdom, U.S., Germany and the Netherlands. It is sold in over forty countries. The book was adapted as a motion picture directed by Richard LaGravenese and starring Hilary Swank and Gerard Butler. It was released in the United States on 21 December 2007.
Her second book, Where Rainbows End (U.S. Love, Rosie), also reached number 1 in Ireland and the UK, and won the German CORINE Award in 2005. It was adapted as a motion picture titled Love, Rosie which was released in 2014, directed by Christian Ditter and starring Lily Collins and Sam Claflin.
She has contributed to charity books with the royalties from short stories such as Irish Girls are Back in Town and Ladies' Night.
Cecelia was the co-creator with (along with Donald Todd) and producer of the ABC comedy Samantha Who? starring Christina Applegate, Jean Smart, Jennifer Esposito, Barry Watson, Kevin Dunn, Melissa McCarthy and Tim Russ.
Her book The Gift was published just before Christmas 2008 in the UK. Her following book, The Book of Tomorrow, was published on the 1 October 2009. In 2016, Cecelia released Flawed, her first book for young adults, and Lyrebird.
Cecelia was nominated for Best Newcomer 2004/5 at the British Book Awards for her debut novel PS, I Love You. She won the 2005 Irish Post Award for Literature and a 2005 Corine Award for her second book Where Rainbows End, (Fur Immer Viellecht) which was voted for by German readers. In 2006, she was long-listed for the IMPAC award for PS I Love You. Cosmopolitan US honoured her with a Fun Fearless Fiction Award 2007 for If You Could See Me Now. Irish Tatler awarded her Writer of the Year at the Woman of the Year awards in 2009. Cecelia’s fifth novel Thanks for the Memories was nominated for Most Popular Book in the British Book Awards 2008. Cecelia was voted Author of Year in the UK Glamour Women of the Year Awards in 2008.