Complete Financial Services, Inc

The regulation was scheduled to take effect on Dec. 1. It would raise the salary limit below which workers automatically qualified for overtime pay to $47,476 from $23,660.

The judge, Amos L. Mazzant III of the Eastern District of Texas, ruled that the Obama administration had exceeded its authority by raising the overtime salary limit so significantly. The ruling was hailed by business groups who argued the new rules would be costly and result in fewer hours for workers.

The Labor Department said it “strongly disagreed” with the decision and was “considering all of our legal options,” raising the possibility of an appeal in the waning days of the Obama administration. Ross Eisenbrey of the Economic Policy Institute, whose writings on the subject helped shape the administration’s regulation, called the ruling “a disappointment to millions of workers who are forced to work long hours with no extra compensation.”

While the injunction is only a temporary measure that suspends the regulation until the judge can issue a ruling on the merits, many said the judge’s language indicated he was likely to strike down the regulation.

“We are, assuming that this preliminary injunction holds and there isn’t an appeal or some other thing that disrupts it, done with this regulation,” said Marc Freedman, executive director of labor law policy at the U.S. Chamber of Commerce, which had challenged the rule.

The fate of the regulation had already been thrown into question by the election of Donald J. Trump as president two weeks ago. Mr. Trump has promised to reverse many regulations approved during the Obama administration, and the Republican Congress has generally criticized the scope of the expansion of overtime eligibility.