A jury decided in 2010 that Disney hid the show's profits from its creators, London-based Celador International. The ruling Monday by a three-judge panel of the 9th U.S. Circuit Court of Appeals found no issues with the verdict or with a judge's rulings in the case.
"I am pleased that justice has been done," Celador Chairman Paul Smith said in a statement.
Disney did not immediately comment on the decision.
The ruling comes more than two years after the jury ruled in Celador's favour after a lengthy trial that featured testimony from several top Disney executives. Celador sued in 2004, claiming Disney was using creative accounting to hide profits from the show, which first ran in the United States from August 1999 to May 2002 and was a huge hit for ABC.
The jury found that Celador was owed $269.2 million, and a judge later added $50 million in interest to the judgment.
The appeals court determined the verdict was not "grossly excessive or monstrous" and that it was not based on speculation or guesswork.