A three-judge panel of the US Court of Appeals for the District of Columbia Circuit on Friday kept most of the restrictions imposed by the original order, but lifted the prohibition on Trump personally criticising Special Counsel Jack Smith, who is overseeing the prosecution.
The court also narrowed the limits on what Trump can say about witnesses in the case, barring only comments about their involvement in the investigation and their potential testimony at trial.
"We agree with the district court that some aspects of Mr. Trump's public statements pose a significant and imminent threat to the fair and orderly adjudication of the ongoing criminal proceeding," Judge Patricia Millett wrote in the order.
But the court found the initial gag order "sweeps in more protected speech than is necessary".
Trump challenged the order as an infringement on his right to free speech under the US Constitution, especially as he campaigns for president as the frontrunner for the 2024 Republican nomination.
"President Trump will continue to fight for the First Amendment rights of tens of millions of Americans to hear from the leading presidential candidate at the height of his campaign," a Trump campaign spokesperson said following the ruling.
A spokesperson for Smith declined to comment.
The case is due to go to trial in Washington in March. Trump has pleaded not guilty.
While placing some limits on Trump, US District Court Judge Tanya Chutkan's gag order allowed him to keep up his drumbeat of accusations against the Justice Department, which he accuses of trying to harm him politically.
Trump has called Smith a "deranged lunatic" and a "thug", among other insults. The appeals court found that Smith "is no more entitled to protection from lawful public criticism" than the Justice Department as a whole.
Chutkan, who is overseeing the case, imposed the gag order on October 16 after she found that Trump's statements on social media and at campaign rallies could influence witnesses and lead to threats against people involved in the case.
The order was suspended while Trump's lawyers appealed, but the narrower version ordered by the appeals court will be reinstated.
Smith's indictment accuses Trump and his allies of promoting false claims that the election was rigged, pressuring officials to alter voting results and assembling fake slates of electors to prevent Congress from certifying Biden's victory.
Trump has also pleaded not guilty in three other criminal cases, including a case brought in Georgia state court that also charges him with unlawfully conspiring to undo the 2020 results.
Trump faces a gag order in a separate civil fraud case in New York barring him from commenting on court staff. He is appealing that order.
