Whilst still in College, Colm was invited to join the Aontas Choral Ensemble, the touring choir of Irish music group Celtic Woman.

In May 2012, Colm was invited by producer Sharon Browne to join Celtic Thunder and first performed with the group in June of that year at Harrah's Resort and Casino in Atlantic City, New Jersey.

He has subsequently toured the United States and Canada numerous times as a principal member of the group, including a special one-off 'unplugged' concert in New York during December 2012, which raised approximately $50,000 in aid of the victims of Hurricane Sandy.

In mid 2014, Colm teamed up with Celtic Thunder cellist (and future wife) Laura Durrant to release a debut single of the Tony Arata song "The Dance".

In, 2015 Colm released another single, this time recording with his brothers the Irish classic "Raglan Road", which rose to #1 on the iTunes World music charts.