Cullinan's poetry collections include The Horizon Forty Miles Away (1973), Today Is Not Different (1978), The White Hail in the Orchard (1984) and Selected Poems 1961 - 1991 (1992).

The volume The White Hail in the Orchard contains what Cullinan called 'versions' by which he meant loose translations from the Italian poetry of Eugenio Montale.

Cullinan's poetry, often (in his earlier works) permeated by the Transvaal landscape, is most often concerned with the personal rather than the political; with emotional and metaphysical themes, such as his poem "My Predawn Owl".

While he was inspired and informed by such European tradition, Cullinan firmly identified himself as an African writer: I spent seven years, from the age of 14 to 21 in Europe (mainly, because I had no choice, in England), so I certainly ingested a great deal of European-ness.

"[2]In addition to volumes of his poetry, Cullinan also published a biography of Robert Jacob Gordon (a Dutch traveller and soldier): Robert Jacob Gordon 1743 - 1795: The Man and His Travels at the Cape (1992), a semi-autobiographical work of prose fiction: Matrix (2002), and most recently, a collection of the letters of Bessie Head: The Imaginative Trespasser (2005).

Cullinan made a significant contribution to South African poetry through his encouragement of young writers, both through his teaching, and through his willingness to mentor, support and constructively criticise.

During his time at Oxford, he was similarly mentored by John Betjeman (who became a significant correspondent,[5]) - and so represented a unique link between a lyrical English verse tradition and following generations of English-speaking South African poets.