While O'Hara's poetry is generally autobiographical, it tends to be based on his observations of New York life rather than exploring his past. In his introduction to The Collected Poems of Frank O’Hara, Donald Allen says "that Frank O’Hara tended to think of his poems as a record of his life is apparent in much of his work.” O'Hara discussed this aspect of his poetry in a statement for Donald Allen's New American Poetry:
What is happening to me, allowing for lies and exaggerations which I try to avoid, goes into my poems. I don’t think my experiences are clarified or made beautiful for myself or anyone else, they are just there in whatever form I can find them. . .My formal "stance" is found at the crossroads where what I know and can't get meets what is left of that I know and can bear without hatred. . .It may be that poetry makes life's nebulous events tangible to me and restores their detail; or conversely that poetry brings forth the intangible quality of incidents which are all too concrete and circumstantial. Or each on specific occasions, or both all the time.
His initial time in the Navy, during his basic training at Sampson Naval Training Center in upstate New York, along with earlier years spent at St. John’s High School began to shape a distinguished style of solitary observation that would later inform his poems. Immersed in regimented daily routine, first Catholic school then the Navy, he was able to separate himself from the situation and make witty and often singular studies. Sometimes these were cataloged for use in later writing, or, perhaps more often, put into letters. This skill of scrutinizing and recording during the bustle and churn of daily life would, later, be one of the important aspects that shaped O’Hara as an urban poet writing off the cuff.
Among his friends, O'Hara was known to treat poetry dismissively, as something to be done only in the moment. John Ashbery claims he witnessed O'Hara “Dashing the poems off at odd moments – in his office at the Museum of Modern Art, in the street at lunchtime or even in a room full of people – he would then put them away in drawers and cartons and half forget them.”
In 1959, he wrote a mock manifesto (originally published in Yugen in 1961) called Personism: A Manifesto, in which he explains his position on formal structure: "I don't ... like rhythm, assonance, all that stuff. You just go on your nerve. If someone's chasing you down the street with a knife you just run, you don't turn around and shout, 'Give it up! I was a track star for Mineola Prep.'" He says, in response to academic overemphasis on form, "As for measure and other technical apparatus, that's just common sense: if you're going to buy a pair of pants you want them to be tight enough so everyone will want to go to bed with you. There's nothing metaphysical about it." He claims that on August 27, 1959, while talking to LeRoi Jones, he founded a movement called Personism which may be "the death of literature as we know it."
"It does not have to do with personality or intimacy, far from it! But to give you a vague idea, one of its minimal aspects is to address itself to one person (other than the poet himself), thus evoking overtones of love without destroying love's life-giving vulgarity, and sustaining the poet's feelings toward the poem while preventing love from distracting him into feeling about the person."
His poetry shows the influence of Abstract Expressionism, Surrealism, Russian poetry, and poets associated with French Symbolism. Ashbery says, “The poetry that meant the most to him when he began writing was either French – Rimbaud, Mallarmé, the Surrealists: poets who speak the language of every day into the reader’s dream – or Russian – Pasternak and especially Mayakovsky, for whom he picked up what James Schuyler has called the ‘intimate yell.’” As part of the New York School of poetry, O'Hara to some degree encapsulated the compositional philosophy of New York School painters.
Ashbery says, “Frank O'Hara's concept of the poem as the chronicle of the creative act that produces it was strengthened by his intimate experience of Pollock's, Kline's, and de Kooning's great paintings of the late '40s and early '50s and of the imaginative realism of painters like Jane Freilicher and Larry Rivers.”
O'Hara was also influenced by William Carlos Williams. According to Marjorie Perloff in her book Frank O'Hara, Poet among Painters, he and Williams both use everyday language and simple statements split at irregular intervals. Perloff points out the similarities between O'Hara's "Autobiographia Literaria" and Williams's "Invocation and Conclusion." At the end of "Autobiographia Literaria," the speaker says, "And here I am, the/center of all beauty!/writing these poems!/Imagine!" Similarly, Williams at the end of "Invocation and Conclusion" says, "Now look at me!" These lines show a shared interest in the self as an individual who can only be himself in isolation. A similar idea is expressed in a line from Williams's "Danse Russe": "Who shall say I am not/ the happy genius of my household?"