Shields was born in Dublin to parents Adolphus Shields, a Church of Ireland left-wing journalist, and Fabby Shields (née Ungerland), a self-described agnostic originally from Hamburg, Germany.

A member of F Company, 2 Battalion, Dublin Brigade, Irish Volunteers since 1914, Shields served with the GPO garrison during Easter Week at outposts in the Hibernian Bank, the Dublin Bread Company building, and the Irish School of Wireless Technology before withdrawing to the GPO. Arrested at the surrender, he was interned in Frongoch until August 1916.

Brother of actor Barry Fitzgerald (born William Shields), Arthur was a leading actor at the Abbey Theatre for over 20 years, starring in about 350 plays from 1914 to 1939. Moving to Hollywood, he became one of the leading supporting actors, appearing in John Ford films such as The Quiet Man (1952), How Green Was My Valley (1941), and She Wore a Yellow Ribbon (1949) and other features like Drums Along the Mohawk (1939).

His final film and television roles were in the early 1960s. He died in Santa Barbara, California, in 1970 aged 74.

[Further Refs: Dictionary of Irish Biography (DIB) entry and Jimmy Wren, The GPO Garrison Easter Week 1916: A Biographical Dictionary (2015)].