Mahon was born the only child of Ulster Protestant working class parents. His father and grandfather worked at Harland and Wolff while his mother worked at a local Flax Mill. During his childhood, he claims he was something of a solitary dreamer, comfortable with his own company yet aware of the world around him. Interested in literature from an early age, he attended Skegoneil Primary school and then the Royal Belfast Academical Institution. At Inst he encountered fellow students who shared his interest in literature and poetry. The school produced a magazine to which Mahon produced some of his early poems. According to the critic Hugh Haughton his early poems were highly fluent and extraordinary for a person so young.
Mahon pursued third level studies at Trinity College, Dublin where he edited Icarus, and formed many friendships with writers such as Michael Longley, Eavan Boland and Brendan Kennelly. He started to mature as a poet. He left Trinity in 1965 to take up studies at the Sorbonne in Paris.
After leaving the Sorbonne in 1966 he worked his way through Canada and the United States. In 1967 he published his first collection of poems Night Crossing. He taught in a school in Dublin and worked in London as a free lance journalist. He currently lives in Kinsale, Co. Cork. On 23 March. 2007 he was awarded the David Cohen Prize for Literature.
Thoroughly educated and with a keen understanding of literary tradition, Mahon came out of the tumult of Northern Ireland with a formal, moderate, even restrained poetic voice. In an era of free verse, Mahon has often written in received forms, using a broadly applied version of iambic pentameter that, metrically, resembles the “sprung foot” verse of Gerard Manley Hopkins. Some poems rhyme. Even the Irish landscape itself is never all that far from the classical tradition, as in his poem “Achill”:
Croagh Patrick towers like Naxos over the water
And I think of my daughter at work on her difficult art
And wish she were with me now between thrush and plover,
Wild thyme and sea-thrift, to lift the weight from my heart.
He has also explored the genre of ekphrasis: the poetic reinterpretation of visual art. In that respect he has been interested in 17th century Dutch and Flemish art.
Mahon has been cited as a major influence by a number of Irish poets, including Seamus Heaney, Eavan Boland and Eamon Grennan.