The Washington Post said Friday previously confidential files show Harvey, who died at the age of 90 last February, was in regular contact with Hoover and would provide the FBI official with advance radio scripts for critiques.
Hoover, meanwhile, would assist Harvey with his radio scripts and research, records show.
The records released as part of a Freedom of Information Act request by the Post also reveal Harvey and Hoover first crossed paths in 1951 when Harvey was caught trying to enter Argonne National Laboratory.
After a federal grand jury decided not to indict Harvey, the journalist was introduced to Hoover by then-U.S. Rep. Fred Busbey, R-Ill., and the pair's friendship began.
The Post said the friendship between the law enforcement official and the radio journalist continued until Hoover died at the age of 77 in 1972.