Fallon is born in Athenry, County Galway on January 3, 1905. His upbringing and his early impressions of the town and the surrounding landscape are intimately described in his poetry. After passing the civil service exams in 1923 he moves to Dublin to work in the Customs House. In Dublin he becomes part of the circle of George William Russell (Æ) who encourages his literary ambitions and arranges for the publication of his early poetry. He forms close friendships with Seumas O’Sullivan, editor of The Dublin Magazine, the poets Austin Clarke, Robert Farren, F.R. Higgins and Patrick McDonagh, and later the novelist James Plunkett.
In 1939, Fallon leaves Dublin to serve as a Customs official in County Wexford, living in Prospect House, near Wexford with his wife, Dorothea (née Maher) and his six sons. During this time he becomes a close friend of the painter Tony O’Malley.
Fallon’s early poetry, short stories and literary criticism are published in The Dublin Magazine and The Bell. He is a regular contributor to Raidió Éireann in the 1940s and 1950s, serving variously as a journalist, scriptwriter and literary critic. A number of his short stories and early dramatic pieces are broadcast by the station during the 1940s. The first of his verse plays for radio, Diarmuid and Gráinne, is broadcast by Raidió Éireann in November 1950. This is followed by The Vision of Mac Conglinne (1953), Two Men with a Face (1953), The Poplar (1953), Steeple Jerkin (1954), The Wooing of Étain (1954), A Man in the Window (1955), Outpost (1955), Deirdre’s King (1956), The Five Stations (1957), The Hags of Clough (1957), The Third Bachelor (1958), At the Bridge Inn (1960) and Lighting up Time (1961).
Three plays adapted from Irish mythology, Diarmuid and Gráinne, The Vision of Mac Conglinne and Deirdre’s King, receive particular contemporary critical acclaim. The landscape, mythology and history of Ireland, interwoven with classical themes and religious symbolism, are frequent themes in his poetry and dramatic works. A number of Fallon’s radio plays are later broadcast on BBC Third Programme and, in translation, in Germany, the Netherlands, and Hungary. The play The Seventh Step is staged at The Globe Theatre in Dublin in 1954. A second one, Sweet Love ’till Morn, is staged at the Abbey Theatre in 1971. He also writes dramatic pieces for television such as A Sword of Steel (1966) and The Fenians (1967), the latter produced by James Plunkett. In a number of his plays and radio dramas he cooperates with contemporary composers providing incidental music, an example being The Wooing of Étain (1954) with music by Brian Boydell.
Fallon retires from the Civil Service in 1963, returning to Dublin before moving to Cornwall in 1967 to live with his son, the sculptor Conor Fallon and his daughter-in-law, the artist Nancy Wynne-Jones. He and his wife return to Ireland in 1971. He spends his last years in Kinsale. He is visiting his son Ivan Fallon in Kent at the time of his death.
While Fallon’s poetry had previously appeared in The Dublin Magazine, The Bell, The Irish Times and a number of anthologies, his first volume of collected poetry, Poems, incorporating a number of previously unpublished poems, is not produced until 1974, months before his death. Three volumes of his poetry, edited by his son, the journalist and critic Brian Fallon, are published after his death: Poems and Versions in 1983, Collected Poems in 1990, and A Look in the Mirror and Other Poems in 2003. In 2005, three of his verse plays, The Vision of Mac Conglinne, The Poplar, and The Hags of Clough, are published in a single volume. A selection of his prose writings and criticism edited by Brian Fallon, A Poet’s Journal, is published in the same year.