Alex Brown of the FBI's records management division said the FBI would post some 2,000 pages of previously secret pages about the Massachusetts Democrat on the agency's website.
The release of the documents has been highly anticipated by historians, scholars and others interested in the life and long public career of one of America's most prominent and powerful politicians.
The Associated Press and other media organizations requested the documents through Freedom of Information Act requests.
Kennedy faced death threats when he ran for president in 1980 and before that in the years following the assassinations of his older brothers.
President John F. Kennedy was assassinated in Dallas on Nov. 22, 1963. U.S. Sen. Robert F. Kennedy was slain in Los Angeles on June 6, 1968.
The deaths of his two older brothers cast a long shadow on Kennedy's life, and prompted fears he too would be targeted by an assassin's bullet.
After his brothers' assassinations, Kennedy wrote in his memoir "True Compass" released last year, that he was easily startled at loud sounds, and would hit the deck whenever a car backfired.
Kennedy, who served in the Senate for nearly half a century, died in August 2009 after a yearlong struggle with brain cancer. He was 77 and the last surviving brother of the famed political family.