Justice Arthur Engoron imposed the gag order on October 3 after Trump accused Engoron's top clerk of political bias in a post on his Truth Social platform. The post left the court "inundated" with hundreds of threats from Trump supporters, Engoron said in a court filing.
An appeals court judge had temporarily paused the order on November 16.
Trump, the frontrunner for the 2024 Republican presidential nomination, is accused in the case brought by New York's attorney general of inflating his net worth by billions of dollars to dupe lenders and insurers.
Trump has denied wrongdoing and said New York Attorney General Letitia James, an elected Democrat, is politically biased against him.
The order was paused while Trump's lawyers appealed, arguing it infringed on his right to free speech under the US Constitution.
A representative of the attorney general's office declined to comment on the order being reinstated on Thursday, and Trump's lawyers did not immediately respond to inquiries.
Engoron had said in his written gag order that the court had been "inundated with hundreds of harassing and threatening phone calls, voicemails, emails, letters, and packages" since Trump's post.
He has already fined Trump $US15,000 ($A22,612) for twice violating the order and warned that future breaches would be met with steeper penalties, including imprisonment.
The gag order only applies to Engoron's staff.
Trump is under a similar gag order in an unrelated criminal case over his efforts to change the results of the 2020 election.
James has said Trump, his adult sons and 10 of his businesses manipulated financial statements to dupe banks and insurers into providing more favourable loan and insurance terms.
The trial largely concerns damages, because Engoron has already found that Trump's financial statements were fraudulent.
James is seeking $US250 million ($A377 million) in penalties, and wants Trump banned from New York state real estate business.
Trump faces four unrelated federal and state criminal indictments, including two over his efforts to overturn the results of the 2020 presidential election.
He has pleaded not guilty in all of those cases.
None of them have dented his commanding lead in the race for the Republican nomination to challenge Democratic President Joe Biden in next November's election.
