Postman was born and spent most of his life in New York City. In 1953, he graduated from State University of New York at Fredonia where he played basketball. He received a master's degree in 1955 and an Ed.D in 1958, both from the Teachers College, Columbia University, and started teaching at New York University (NYU) in 1959. In 1971, he founded a graduate program in media ecology at the Steinhardt School of Education of NYU.
In 1993 he was appointed a University Professor, the only one in the School of Education, and was chairman of the Department of Culture and Communication until 2002. Among his students were authors Paul Levinson, Joshua Meyrowitz, Jay Rosen, Lance Strate, and Dennis Smith.
Postman wrote 18 books and more than 200 magazine and newspaper articles for such periodicals as The New York Times Magazine, The Atlantic Monthly, Harper's, Time Magazine, The Saturday Review, The Harvard Education Review, The Washington Post, Los Angeles Times, Stern, and Le Monde. He was the editor of the quarterly journal ETC.; A review of General Semantics (founded by S.I. Hayakawa in 1943) from 1976 to 1986. He was also on the editorial board of The Nation.