Barry was admitted to the Irish Bar in 1848 and was appointed Queen's Counsel in 1859. He was Member of Parliament for Dungarvan from 1865 to 1868, He was appointed Law Adviser to the Lord Lieutenant of Ireland in 1865, and was made Third Serjeant-at-law (Ireland) in 1866. He served as Solicitor-General for Ireland from 1868 to 1870, and as such prosecuted the Fenians in 1868. From 1870 to 1872 he was Attorney-General for Ireland. In 1872 Barry was appointed a Justice of the Queen's Bench and from 1883 to 1897 served as Lord Justice of the Irish Court of Appeal. Elrington Ball attributed his rise not only to his extraordinary legal ability, but also his immense personal popularity.