Born and raised in Pittsburgh, Pennsylvania, U.S.'s neighborhood of East Liberty, he attended Peabody High School then worked as a door-to-door salesman, an exterminator, and a steelworker. He graduated from the University of Pittsburgh, where he and his classmate Gerald Stern developed a serious interest in poetry and writing. His work is distinguished by simple lyricism and straightforward clarity of tone. Though his first book of poetry (Views of Jeopardy, 1962) was quickly recognized and Gilbert himself made into something of a media darling, he retreated from his earlier activity in the San Francisco poetry scene (where he participated in Jack Spicer's Poetry as Magic workshop) and moved to Europe, touring from country to country while living on a Guggenheim Fellowship. Nearly the whole of his career after the publication of his first book of poetry is marked by what he has described in interviews as a self-imposed isolation—which some have considered to be a spiritual quest to describe his alienation from mainstream American culture, and others have dismissed as little more than an extended period as a "professional houseguest" living off of wealthy American literary admirers. Subsequent books of poetry have been few and far between. He continued to write, however, and between books has occasionally contributed to The American Poetry Review, Genesis West, The Quarterly, Poetry, Ironwood, The Kenyon Review, and The New Yorker. He was a close friend of the poet Linda Gregg who was once his student and to whom he was married for six years. He was also married to Michiko Nogami (a language instructor based in San Francisco, now deceased, about whom he has written many of his poems). He was also in a significant long term relationship with the Beat poet Laura Ulewicz during the fifties in San Francisco.