O’Dea, born James Augustine O’Dea, is one of eleven children of James O’Dea, an ironmonger, and Martha O’Gorman, who keeps a small toy shop. His father has a shop in Capel Street. He is educated at the Irish Christian Brothers O’Connell School in North Richmond Street, Dublin, where a classmate is future Taoiseach Seán Lemass, by the Holy Ghost Fathers at Blackrock College, and by the Jesuits at Belvedere College. From a young age he is interested in taking to the stage. He co-founds an amateur acting group, the Kilronan Players, in 1917, but his father will not hear of it. He is apprenticed to an optician in Edinburgh, Scotland, where he qualifies as an optician.
O’Dea returns to Dublin where, at age 21, he sets up his own business which he eventually gives to his sister, Rita. In his spare time he takes part in amateur productions of Henrik Ibsen and Anton Chekhov. From 1920 he is in the Irish theatre in Hardwicke Street working with actor-producer John MacDonagh. In 1922 he makes a series of comedy films for Norman Whitten. After working in plays by George Bernard Shaw for a few years he rejoins MacDonagh in revues, the first of which, Dublin To-Night, is produced at the Queen’s Theatre, Dublin in 1924. In 1927 he takes to the stage full-time. In 1928, the company’s first production Here We Are wins international acclaim, and in December of the same year it produces its first Christmas Pantomime, Sinbad the Sailor.
O’Dea forms a partnership with Harry O’Donovan whom he first meets in a production of You Never Can Tell in 1924. Their first show is Look Who’s Here at Queen’s Theatre. For more than two decades beginning in 1929 the duo produces two shows a year in Dublin, first in the Olympia Theatre, then in the Gaiety Theatre. They create O’Dea’s most famous character, Mrs. Biddy Mulligan. The role draws on O’Dea’s previous manifestations as “Dames” in Variety performances and pantomimes. Biddy Mulligan is the representation (caricature, parody and stereotype) of a Dublin street-seller, with all the working-class repartee, wisdom and failings implicit. He makes a number of recordings of sketches starring Mrs. Mulligan. Biddy Mulligan is referenced in many Dublin music hall songs such as “Biddy Mulligan the Pride of the Coombe,” “Daffy the Belle of the Coombe” and “The Charladies’ Ball.”
O’Dea makes some film appearances, such as Darby O’Gill and the Little People (1959) in which he plays King Brian of the little people and Johnny Nobody (1961). He also has a successful career in pantomime and tours Ireland and England many times, and is much associated with actress Maureen Potter, with whom he often partners.
O’Dea is also a prolific songwriter in his day. Many of his songs are still well known to this day, some of them having been sung and recorded by Dublin singer Frank Harte.
O’Dea marries Ursula Doyle, a theatrical impresario, in September 1959 with Seán Lemass standing in as best man and Maureen Potter as the bridesmaid. O’Dea had been best man at Lemass’s wedding in 1924.
Jimmy O’Dea dies at Dr. Steevens’ Hospital, Dublin, at age 65, on January 7, 1965. Seán Lemass, at the time Taoiseach, gives the valedictory oration at his funeral. He is buried in Glasnevin Cemetery, Dublin.