According to CNN, the judgement from U.S. District Judge John A. Kronstadt in California, Thicke, Williams and Williams' More Water From Nazareth Publishing are required to pay Gaye's family damages of almost $2.9 million.
Reps for Thicke and Williams could not be reached for comment.
The duo appealed after Gaye's family initially won the case back in 2015.
In addition, Gaye's family will be entitled to 50% of any future royalties earned by "Blurred Lines", which was the biggest-selling single around the world in 2013.
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The judgment has been controversial, with Williams arguing for "Feel". Thicke additionally was arranged to pay more than $1.7 million and Williams and his distributing company must pay $357,631 to Gaye's home.
As the BBC reported, the appeals court was also split.
A California court upheld the verdict in March this year, and the new amended judgement has since confirmed the settlement. The damages will paid by Williams and Thicke themselves and the former's publishing entity More Water From Nazareth.
But, Richard Busch, the lawyer representing Gaye's family, said the decision "not only protects songwriters' works from being unlawfully copied without payment or credit, but encourages today's writers to create original work that does not take advantage of the success of others while pawning it off as their own".
Circuit Judge Jacqueline Nguyen said the two songs "differed in melody, harmony and rhythm" and wrote that the verdict "strikes a devastating blow to future musicians and composers everywhere".