The decision is a win for Lisa Cook, the Federal Reserve governor whom President Trump sought to dismiss over allegations of mortgage fraud.

A federal judge late Tuesday temporarily blocked President Trump from removing Lisa Cook from the Federal Reserve’s Board of Governors, allowing her to continue serving as she contests her recent dismissal.

The decision dealt a blow to Mr. Trump, who had tried to fire Ms. Cook over allegations that she had falsified documents related to her mortgages, even though she had not been charged or convicted of a crime. Lawyers for Ms. Cook have framed her attempted ouster as politically motivated, citing the president’s desire to appoint loyalists to the Fed who will cut interest rates as he desires.

The decision from Judge Jia M. Cobb of the U.S. District Court for the District of Columbia marked only the first salvo in what is likely to be a lengthy legal battle over the president’s ability to remove a Fed official “for cause,” a term generally understood to mean professional neglect or wrongdoing.

In her ruling, Judge Cobb said Mr. Trump’s justifications for removing Ms. Cook did not meet the threshold for sufficient cause, in part because the action in question took place before her tenure as a Fed governor began. Ms. Cook signed her mortgage documents in 2021, roughly a year before she joined the Fed after being appointed by President Joseph R. Biden Jr.

“The best reading of the ‘for cause’ provision is that the bases for removal of a member of the Board of Governors are limited to grounds concerning a governor’s behavior in office and whether they have been faithfully and effectively executing their statutory duties,” she said. “‘For cause’ thus does not contemplate removing an individual purely for conduct that occurred before they began in office.”

Lawyers at the Justice Department argued in their first hearing that the president had expansive powers to determine what constitutes cause and that the court should be “highly deferential” to that interpretation.

Judge Cobb hit back at that assertion directly in her ruling. “According to the government, the determination of cause is committed to the president’s discretion by statute, leaving no role for this court. The court disagrees,” she said.

Ms. Cook also was denied adequate due process, Judge Cobb argued, agreeing with a central part of her lawyers’ argument.

“Today’s ruling recognizes and reaffirms the importance of safeguarding the independence of the Federal Reserve from illegal political interference,” said Ms. Cook’s lawyer, Abbe Lowell. “Allowing the president to unlawfully remove Governor Cook on unsubstantiated and vague allegations would endanger the stability of our financial system and undermine the rule of law.”

The Trump administration is likely to appeal the ruling. In a statement, Kush Desai, a spokesman for the White House, said the president had “lawfully removed” Ms. Cook, adding: “This ruling will not be the last say on the matter, and the Trump administration will continue to work to restore accountability and confidence in the Fed.”

The judge’s order means that Ms. Cook will be able to cast a vote when the Fed gathers for its next two-day meeting, which will begin on Tuesday. The central bank is expected to restart interest rate cuts that have been on hold since January, most likely reducing borrowing costs a quarter point.

The Fed declined to comment on the ruling. It had previously pledged to carry out any decision rendered by the court.

“Removal protection is an important measure that helps insulate the Fed from inappropriate political interference,” said Graham Steele, a longtime financial regulation lawyer and former Treasury Department official. “The court’s thorough and well-reasoned decision reaches the right conclusion.”

Mr. Trump has sought to force down borrowing costs for months, accusing Jerome H. Powell, the Fed chair, and other officials at the central bank of harming the economy by not moving quickly enough to cut rates. The Fed has kept its benchmark rate set in a range of 4.25 to 4.5 percent since January. Mr. Trump has called on the Fed to slash borrowing costs by three percentage points.

The president is seeking to gain a majority of support on the Fed’s board, which would give him not only greater sway over deliberations related to interest rates and the oversight of Wall Street but also leverage over the 12 regional Fed presidents, who vote on big policy decisions on a rotating basis, as well as the central bank’s staff.

In its ruling, the court declined to take up the issue of Mr. Trump’s motivation for firing Ms. Cook.