Agnew was born to Irish entertainer Adele King and Irish oboist David Agnew. She made her first television appearance on her mother's programme at just four weeks old, and subsequently sang on the show at the age of six.

In 1998, Agnew represented Ireland and was the winner of the Grand Prix at the First International Children's Song Competition in Cairo, Egypt, with a song called "The Friendship Tree". She then began to perform pantomime at the Olympia Theatre in Dublin and continued in that role for four years.

In 1999, she appeared in The Young Messiah, a modern adaptation of Handel's Messiah. In this production, she played one of the children and performed sign language.

In 2000, at age 11, Agnew approached director David Downes about recording a song to raise money for the children of Afghanistan. With his assistance, she recorded "Angel of Mercy" for the album This Holy Christmas Night, which raised over GB£20,000 for the Afghan Children's Charity Fund in 2001. During this year, she joined the Christ Church Cathedral Girls' Choir, and remained a member for three years.

In 2002, at 12 years of age, Agnew was signed to Celtic Collections, and with the backing of Downes she recorded her debut album Chloë. Two years later, in 2004, she followed this with her second album, Chloë: Walking in the Air. That same year, she appeared as part of the group Celtic Woman at The Helix in Dublin. To date, she has recorded three albums with the group and has taken part in several world tours.

--Wikipedia