The lawsuit in federal court in Manhattan seeks unspecified damages and a court declaration Belafonte is the rightful owner.
The documents are an outline of a Vietnam War speech by King, notes to a speech King never got to deliver in Memphis, Tenn., and a condolence letter from President Lyndon B. Johnson to King's wife after the civil rights leader's 1968 assassination.
According to the lawsuit, Belafonte was preparing to auction the items in 2008 when the estate "astonishingly" blocked it.
The lawsuit cited the close relationship between Belafonte and King, saying the pair "worked on strategies and collaborated on issues that would transform American society" while they "forged a deep and enduring personal friendship." It said King and his widow, Coretta Scott King, gave Belafonte a number of items and it noted that Coretta Scott King, who died in 2006, mentioned Belafonte in her autobiography, saying "whenever we got into trouble or when tragedy struck, Harry has always come to our aid, his generous heart wide open."
Belafonte said he delivered the documents for auction to Sotheby's Inc. in early 2008 and the auction house has held them pending a resolution of the dispute between the estate and Belafonte.
The lawsuit said Belafonte had held the Vietnam War speech outline since 1967, when King left it behind after working on it in Belafonte's apartment. It said the Memphis speech notes were found in King's suit pocket after he was assassinated. According to the lawsuit, Coretta Scott King offered the notes to Belafonte but he suggested they instead be given to one of King's longest-serving confidants. When that man died in 1979, his widow delivered the notes to Belafonte, it said.
The letter from Johnson was given to Belafonte by Coretta Scott King about a decade ago after she admired the collection of historic documents on a wall of his home, the lawsuit said.
The lawsuit said King frequently gave drafts and copies of his speeches, correspondence and working papers to friends and fellow civil rights activists and that his estate has made a series of "disturbing and illegitimate challenges to Dr. King's gift-giving" in recent years.
Miles J. Alexander, a lawyer for the Atlanta-based King estate, said he had not yet seen the lawsuit.
"I have no comment I can make right now," he said.