When still quite young, Kearns began entering and winning traditional All-Ireland singing competitions. A self-taught musician, he joined the secondary school band and quickly became the resident singer, singing at all the Masses and in school shows. He entered any and all available competitions during his school years as well, and once again, winning came easily.

The turning point in his career came in 1993 when he entered a contest, “Ireland’s Search for a Tenor," in conjunction with the Bank of Ireland’s launch of a new ten pound note commonly called "a tenner." Anthony was the only untrained singer competing, but won the contest after three rounds. Upon winning the competition, Anthony studied for three years at the Leinster School of Music in Dublin with Veronica Dunne, later furthering his studies in Cardiff at the College of Music in Wales.

Kearns went on to win the prestigious Dermot Troy Trophy for oratorio in 1995 and 1996, the Best Male Singer at the Waterford International Festival of Light Opera in 1995, and he reached the top at the ESB Veronica Dunne International Singing Competition in 1999. Anthony was studying in Wales in 1998 when he received the call from the Irish Tenors.

Recognized as Ireland's Finest Tenor, Anthony peformed at and recorded with "Ireland's Finest" at the National Concert Hall, Dublin, for the RTÉ in January, 2007. He has been able to explore his passion for opera by performing with Opera Ireland singing various roles. In April, 2006, he sang the lead in “Faust” in Dublin and sang Rinuccio in “Gianni Schicchi” in 2005. He has sung with Dublin’s Lyric Opera in “La Traviata” and “MacBeth,” as well. Besides his opera work in Ireland, Anthony also sang the role of Fenton in an Italian production of Verdi's "Falstaff" in July, 2002, in Tuscany. He has repeatedly sung lead tenor in the Irish Ring in Ireland and the U.S. Kearns has sung at all the top venues in Ireland including the Gaiety Theatre, Dublin, and The National Concert Halls in Dublin and Limmerick; he has also performed with the National Symphony Orchestra. Anthony was a guest soloist for the Boston Pops, the Chicagoland Pops, and also sang during Good Morning America’s funeral coverage for the late President Reagan.