The district attorney leading a high-profile investigation into former President Donald Trump plans on leaving office later this year.
Vance said he'd essentially made the decision before taking on the Trump case.
The 66-year-old cited the pressure of being the Manhattan district attorney.
"It turned out to be tougher than I thought it would be," he said, adding: "There’s nothing worse than a politician who doesn’t know when to leave."
Vance is conducting a secretive probe of Trump. He has repeatedly declined to shed insight on the investigation, though court filings indicate prosecutors believe the former president may have falsified records and committed fraud.
Trump in a statement said the city "has been looking at almost every transaction I’ve ever done" and asserted the nation's highest court "never should have let this ‘fishing expedition’ happen."
Because of the city's political makeup, Vance's successor is all but assured to be a Democrat.
At least nine candidates are running for the office, including former Manhattan Assistant District Attorneys Liz Crotty, Diana Florence, and Lucy Lang, Assemblyman Dan Quart, and attorney Janos Marton.