Con Colbert was born in Moanleana, County Limerick, fourth youngest of thirteen children. At sixteen he went to live with his sister Catherine in Ranelagh Co. Dublin. Con became a drill instructor at St. Enda's School, founded by Patrick Pearse, while a member of Fianna Éireann.

In 1913 he was an early member of the Irish Volunteers. He also joined the Irish Republican Brotherhood. In the weeks leading up to the Rising, he acted as bodyguard for Thomas Clarke. During Easter Week, he fought at Watkin's Brewery, Jameson's Distillery and Marrowbone Lane. When the order to surrender was issued, Colbert surrendered with the Marrowbone Lane Garrison along with the South Dublin Union Garrison, which had been led by Éamonn Ceannt.

They were marched to Richmond Barracks, where Colbert would later be court-martialled. Transferred to Kilmainham Gaol, Colbert was shot by firing squad the next morning on 8 May 1916.