The special counsel investigating President Biden said in a report released on Thursday that he had decided not to seek prosecution of Mr. Biden over his handling of classified material after leaving the vice presidency in early 2017, but had found evidence that Mr. Biden willfully retained and disclosed some sensitive material.

The report said that Mr. Biden had left the White House after his vice presidency with classified documents about Afghanistan and notebooks with handwritten entries “implicating sensitive intelligence sources and methods” taken from internal White House briefings.

Robert K. Hur, the special counsel, said in his report that Mr. Biden had shared the notebooks with a ghostwriter who helped him on his 2017 memoir, “Promise Me, Dad.”

Mr. Hur, a former Trump Justice Department official appointed by Attorney General Merrick B. Garland in January 2023 to lead the inquiry after classified files were found in the garage and living areas of Mr. Biden’s home in Delaware and his former office in Washington, said his decision not to pursue criminal charges would have been the same even if Justice Department policy did not preclude indicting a sitting president.

“We conclude that the evidence does not establish Mr. Biden’s guilt beyond a reasonable doubt,” wrote Mr. Hur.

Mr. Hur cited Mr. Biden’s cooperation with investigators, in stark contrast with former President Donald J. Trump’s behavior when documents were discovered at his resort in Florida, as one of the factors in his decision not to bring charges.