Holzer was born in Vienna, Austria, the son of Martha (Stransky) and Leo Holzer, a businessman. His interest in the supernatural was sparked at a young age by stories told to him by his uncle Henry. He went on to study archaeology and ancient history at the University of Vienna but being Jewish, his family decided it was unsafe to stay in Austria and left the country for New York City in 1938. He studied Japanese at Columbia University and, after studying comparative religion and parapsychology, claimed to have obtained a Ph.D. at a school called the London College of Applied Science which has never been validated. He went on to teach parapsychology at the New York Institute of Technology. Holzer wrote more than 120 books on ghosts and the afterlife.