But Twitter lost a series of court rulings on the issue, and a judge warned that if it failed to turn over the information by Friday, the company would face substantial fines.
A lower-court judge, noting that Harris's tweets were public, wrote, "There can be no reasonable expectation of privacy in a tweet sent around the world."
The judge also argued that all third parties have the burden of deciding if subpoenas are legitimate and that Twitter shouldn't receive a special exception.
The American Civil Liberties Union (ACLU) filed briefs supporting Twitter and Harris, arguing the tweets are protected under the First and Fourth amendments.
Twitter and the Manhattan District Attorney's Office did not comment.
Malcolm Harris tweeted, "So Twitter handed over a pile of my tweets that'll stay sealed pending a hearing on the 21st. Bummer."