In the 1940s, Lamantia returned to San Francisco and took courses at University of California, Berkeley. He traveled in France, Mexico, northern Africa, and the United States and lived for a while in Spain. During his US travels in the 1950s, he explored the use of peyote with Washoe Native Americans in Nevada.
Lamantia’s surrealist poetry influenced Allen Ginsberg and other Beat poets. The poet Lawrence Ferlinghetti noted of Lamantia’s work, “Philip was a visionary like Blake, and he really saw the whole world in a grain of sand.” Interested in poetry and jazz, Lamantia was a member of a jazz and poetry group with Jack Kerouac, Howard Hart, and David Antrim in the 1950s. In his later years, he returned to the Catholicism of his youth, writing poetry that reflected his rediscovered faith.
Lamantia lectured at San Francisco State University and the San Francisco Art Institute and was married to Nancy Peters, his editor at City Lights Books. He died in 2005.