Eamonn Bulfin was born in Argentina to Irish parents. His father William Bulfin of Derrinlough, near Birr, County Offaly, had emigrated to Argentina in the 1880s and became the editor of The Southern Cross newspaper. On the family's return to Ireland, William Bulfin enrolled Eamonn in Pearse's school, St Enda's in Rathfarnham, and he later attended University College Dublin. Eamonn joined the Irish Republican Brotherhood in 1913, and along with some fellow St Enda's students created home-made bombs in the school's basement in preparation for the Easter Rising.

Notable for raising the 'Irish Republic' flag over the GPO In the Easter Rising of 1916. Following the insurrection he was condemned to death, but was reprieved and deported to Buenos Aires after internment in Frongoch in Wales along with the other Irish soldiers of the Rising. In 1920 he was elected Chairperson of Offaly County Council in absentia and held the post when the decision was taken to rename King's County as Offaly. He returned in 1923 on the establishment of the Irish Free State in 1922 and was active in local politics.