US District Judge Lewis Kaplan announced the decision on Friday at a hearing over Bankman-Fried's bail conditions in federal court in Manhattan.
Federal prosecutors in Manhattan first made their surprise request to jail the former billionaire in a July 26 hearing, saying he "crossed a line" by sharing former romantic partner Caroline Ellison's personal writings with a New York Times reporter.
Bankman-Fried, 31, has pleaded not guilty to stealing billions of dollars in FTX customer funds to plug losses at his Alameda Research hedge fund, where Ellison was chief executive.
His lawyers said prosecutors mischaracterised his intentions in sharing Ellison's writings, arguing he wanted to defend his reputation and that he had a right to speak to the press.
Bankman-Fried has been largely confined to his parents' Palo Alto, California, home on $US250 million ($A383 million) bond since his December 2022 arrest.
In the July 26 hearing, Kaplan restricted Bankman-Fried from speaking publicly about his case, but asked both sides to submit written arguments on whether to detain him.
Ellison and two other former members of Bankman-Fried's inner circle have pleaded guilty to fraud and agreed to cooperate with the US Lawyer's Office in Manhattan. She is expected to testify against him at his scheduled October 2 trial.
In the July 26 hearing, Kaplan restricted Bankman-Fried from speaking publicly about his case, and asked both sides to address whether jail was necessary.
The gag order has drawn attention from news media, including the Times, which in an August 2 letter to the judge said the measure should be loosened to only restrict comments that could interfere with a fair trial.
A July 20 article in the newspaper contained excerpts from Ellison's personal Google documents prior to FTX's collapse.
She described being "unhappy and overwhelmed" with her job and feeling "hurt/rejected" from her personal breakup with Bankman-Fried.
