According to a 1995 interview by Leonard Lieberman, Andrew Lyons and Hariet Lyons in Current Anthropology, Montagu grew up in London's East End. Like many other children, he was often subjected to antisemitic assaults when he ventured from his own Jewish neighborhood. He developed an interest in anatomy very early and as a boy was befriended by Arthur Keith. In 1922, at the age of 17, he entered University College London, where he received a diploma in psychology after studying with Karl Pearson and C.E. Spearman and taking anthropology courses with Grafton Elliot Smith and Charles Gabriel Seligman. He also studied at the London School of Economics, where he became one of the first students of Bronis?aw Malinowski. He pursued postgraduate work at Columbia University, where he produced a dissertation in 1936 entitled Coming into being among the Australian Aborigines: A study of the procreative beliefs of the native tribes of Australia which was directed by Franz Boas and Ruth Benedict. He taught anatomy at various schools in the United States before becoming a professor of anthropology at Rutgers from 1949 to 1955.

In the 1950s Montagu produced a series of works questioning the validity of race as a biological concept, including the UNESCO Statement on Race and his very well-known Man’s Most Dangerous Myth: The Fallacy of Race. He was particularly opposed to the work of Carleton S. Coon. In 1952, together with William Vogt, he gave the first Alfred Korzybski Memorial Lecture, inaugurating the series.

He retired from his academic career in 1955 and moved to Princeton, New Jersey to pursue his popular writing and public appearances. He became a well-known guest on Johnny Carson's Tonight Show. He directed his numerous published studies on the significant relationship of mother and infant to the general public. The humanizing effects of touch informed the studies of isolation-reared monkeys and adult pathological violence that is the subject of his Time-Life documentary "Rock A Bye Baby" (1970).

Later in life, Montagu actively opposed genital modification and mutilation of children. In 1994, James Prescott, Ph.D., wrote and named in honor of Dr. Montagu, who was one of its original signers, the Ashley Montagu Resolution to End the Genital Mutilation of Children Worldwide: A Petition to the World Court, The Hague.

In 1995, the American Humanist Association named him the Humanist of the Year.

Montagu, who became a naturalized American citizen in 1940, taught and lectured at Harvard, Princeton University, Rutgers University, the University of California, and New York University. He wrote over 60 books.

• Life Before Birth
• Touching: The Human Significance of The Skin 1971
• On Being Human
• The Direction of Human Development: Biological and Social Bases
• Culture and human development
• The Nature of Human Aggression
• The Natural Superiority of Women
• Race and IQ
• Living and Loving
• The Anatomy of Swearing
• The Human Connection
• The Peace of The World
• The Fallacy of Race (1942)
• Human Evolution
• Anthropology and Human Nature
• The Elephant Man: A Study in Human Dignity. (1942)
• The Cultured Man
• Man: His first Million Years

• Human Heredity

Montagu wrote the Foreword and Bibliography of the 1955 edition (reprinted 2005) of A Factor of Evolution by Petr Kropotkin, and in 1956, he edited , a critique of Arnold J. Toynbee's seminal A Study of History.

He is co-author with Floyd Matson of The Human Connection and The Dehumanization of Man. He is the writer and director of the film One World or None, described as one of the best documentaries ever made.

Footage of Ashley Montagu talking with Charlton Heston about his character in the movie appears as a bonus in the special DVD edition of The Omega Man. Archive footage of him, among others (including Carl Sagan), is also featured in The X-Files episode Gethsemane.