The National Archives released more than 10,000 pages of records in connection with Kennedy's killing, according to details on its website on Friday.
The move is part of a broader effort by Trump's administration to declassify information about the assassinations of a number of high-profile figures.
The agency previously published records related to 1963 assassination of then-president John F Kennedy, who was killed several years before the senator, his brother.
Robert F Kennedy was fatally shot on June 5, 1968, at the Ambassador Hotel in Los Angeles moments after giving his victory speech for winning California's Democratic presidential primary.
His assassin, Sirhan Sirhan, was convicted of first-degree murder and is serving life in prison.
The files included pictures of handwritten notes by the gunman.
"RFK must be disposed of like his brother was," was written on the outside of an empty envelope with the return address from the district director of the Internal Revenue Service in Los Angeles.
In one of the newly release documents, the assassin said he advocated for "the overthrow of the current president".
Democrat Lyndon Johnson was in the White House at the time of RFK's death.
"I have no absolute plans yet but soon will compose them," wrote Sirhan, who pledged support for communist Russia and China.
FBI documents describe interviews with a group of tourists who had heard rumours about Kennedy being shot weeks before his death.
Several people who visited Israel in May 1968 said a tour guide told them Kennedy had been shot.
One person said he heard that an attempt on Kennedy's life had been made in Milwaukee and another heard that he was shot in Nebraska.
The National Archives and Records Administration posted 229 files containing the pages to its public website.
Many files related to the senator's assassination had been previously released but others had not been digitised and sat for decades in storage facilities maintained by the federal government.
"Nearly 60 years after the tragic assassination of Senator Robert F Kennedy, the American people will, for the first time, have the opportunity to review the federal government's investigation thanks to the leadership of President Trump," Tulsi Gabbard, the director of national intelligence, said in a statement.
Gabbard also said the files release "shine a long-overdue light on the truth".
"Lifting the veil on the RFK papers is a necessary step toward restoring trust in American government," US Health and Human Services Secretary Robert F Kennedy Jr, the senator's son, said in a statement.
The health chief has previously said he believes his father was killed by multiple gunmen, an assertion that contradicts official accounts.
Trump signed an executive order in January calling for the release of governmental documents related to the assassinations of Robert F Kennedy and Martin Luther King Jr, who were killed within two months of each other.
The National Archives did not respond to a request for comment on when to expect the King files or whether more files would be released in connection with the killings of the Kennedy brothers.
with AP
