The family ran a grocery, and after the early death of his father, the business was sold and Ellen re-joined her first profession, nursing.
Tierney began working for Córas Iompair Éireann (CIÉ) shortly after leaving school, and was to become a prominent member of the Irish Transport & General Workers Union, holding the roles of branch secretary and vice-president.
In March 1968 he was guest of honor of Mayor Richard J. Daley of Chicago during the Saint Patrick's Day parade.
On this trip he addressed the United States House of Representatives, and in Boston visited American soldiers wounded in Vietnam.
Tierney spent nineteen years on the corporation, fifteen on the Harbour Board as Commissioner, and a number of other private and public associations.