Kenneth Mackenzie was the grandson of George Paterson, a member of Alexander Forrest's [1879] Kimberley expedition. He was named Kenneth Ivo Brownley Langwell by his overbearing father, Hugh. His mother Marguerite Christina Pryde Paterson (Daisy), after her divorce from Hugh, shortened the name to Kenneth Ivo. Daisy and her two children lived with her parents in South Perth until 1922 when her father bought 'The Cottage' at Pinjarra and the family moved there. Mackenzie loved the surrounding bushland and showed early promise as a musician. After the small state school at Pinjarra, he attended Guildford Grammar School and, in 1930, Muresk Agricultural College where he disliked the coursework but wrote The Young Desire It (published in 1937), with scenes reminiscent of his experiences at Guildford Grammar. He studied arts/law at the University of Western Australia for a short time.
After journalistic work for the West Australian, Mackenzie left Perth in December 1933 for Melbourne where he was lonely and unable to find employment. He moved to Sydney, on the advice of Norman Lindsay. In 1934, he married art teacher Kathleen Bartlett and they had two children, Elizabeth and Hugh. Mackenzie worked in radio and as a journalist with Smith's Weekly and ABC Weekly, before being drafted into the army in 1942. He served as an orderly room corporal in Cowra, overseeing captives in a prisoner of war camp, and later spent time in Concord army hospital. Mackenzie witnessed the mass outbreak of Japanese prisoners from Cowra - written about in his novel Dead Men Rising - withdrawn from circulation soon after its publication.
Douglas Stewart wrote in the Foreword to Selected Poems of Kenneth Mackenzie (1961): '...those of us who knew him in Sydney - I am sure I can speak for Hugh McCrae, Kenneth Slessor, Robert D. Fitzgerald, Ronald McCuaig, as well as myself; anyone who was writing verse in the forties - never doubted for a moment that he [Kenneth Mackenzie] was a poet of the first quality'. Stewart commented on the fastidiousness of form and phrase and the exceptional command of technique in Mackenzie's poetry.
Mackenzie was the recipient of a succession of Commonwealth Literary Fund fellowships. According to sources including the Bulletin (17 May 1939, p.18 ), he used the name Seaforth MacKenzie for his fiction because his publisher, Jonathan Cape, 'already had a Kenneth MacKenzie writing for him.' The Bulletin (23 August 1950) recorded : 'He signs them [his novels] Seaforth Mackenzie, keeping Kenneth Mackenzie for his poems', because he wanted to keep his two reputations, as a poet and as a novelist, separate. In the last years of his life, troubled by ongoing employment problems and alcoholism, he lived at Kurrajong, in the foothills of the Blue Mountains, attempted subsistence farming, gardened and wrote. 'In his last novel the farm cited as the retreat for the fated one was undoubtedly his own domicile' (The Bulletin, Red Page, 23 March 1955). He died by drowning at Tallong Creek near Goulburn, in an incident foreshadowed in a poem, 'Heat', first published in the Bulletin in February 1939. He left behind unpublished manuscripts of short stories, radio plays and two novels. The Oxford Companion to Australian Literature asserts that his later poetry achieved 'a controlled tranquility and compassion'.
