Lamantia was born in San Francisco, California, United States, to Sicilian immigrants and was raised in the city's Excelsior District neighborhood.

He dropped out of Balboa High School to pursue poetry in New York City, and appeared the same year in American filmmaker Maya Deren's At Land.

[1] Gerd Stern, a poet who had met Lamantia at a reading at the San Francisco Museum of Art in 1947, recalled of his friend: "He admired Dylan Thomas and Wallace Stevens.

"[5] Lamantia was also known for his journeys with native peoples in the United States and Mexico, participating in the peyote-eating rituals of the Washo Indians of Nevada, which often inspired his poems.

American writer Nancy Peters, who was Lamantia's wife and literary editor, commented that "he found in the narcotic night world a kind of modern counterpart to the Gothic castle—a zone of peril to be symbolically or existentially crossed.