The Pitch Perfect star was sued by Australian actor Charlotte MacInnes, who played the lead role in Wilson's directorial debut film The Deb.
MacInnes claimed Wilson defamed her in four social media posts that implied she was a liar and a sellout who walked back a sexual harassment complaint to further her career.
The posts alleged the young actor confided in Wilson - and later recanted - that she felt uncomfortable when the film's co-producer Amanda Ghost asked to have a shower and a bath together.
MacInnes denied making or retracting a complaint, insisting she had not been uncomfortable when the pair shared a bath in their swimwear after Ms Ghost suffered a medical episode in September 2023.
Two months after the conclusion of the hotly contested court fight in the Federal Court, Justice Elizabeth Raper found in favour of Wilson.
One of the posts carried the imputation that MacInnes had changed her story but neither that post nor the other three were defamatory, she ruled.
"I do not accept that the assertion of someone changing their story, for which there could be innumerable reasons ... is defamatory," Justice Raper said on Wednesday.
She determined MacInnes had changed her story after bathing with Ms Ghost in the Bondi apartment where they were both staying during filming.
"To say that the circumstances surrounding how they came to be in the bath are unusual would be an understatement," Justice Raper said.
"It is highly probable that any person placed in that position would feel uncomfortable about what had occurred."
A representative for MacInnes told the ABC she plans to lodge an appeal against the decision.
Wilson, who lives in the US and was not present for the judgment, welcomed the successful conclusion of the court battle.
"This has been a long process and throughout I have tried to stay grounded in my values and what I believed was right," she said in a statement.
"I'm thankful that process has now reached its conclusion."
MacInnes' barrister Sue Chrysanthou SC had accused Wilson of a "complete revision of history" during her emphatic closing address in May.
"She is a fantastical liar who has made up terrible, terrible allegations," she said.
"We say Ms Wilson cannot be believed on anything she has said."
But Wilson repeatedly denied accusations she fabricated the complaint or raised it for leverage during disputes with her co-producers over the film's budget and writing credit.
"I am known as a truth-teller," she declared during the hearing.
That was what she had been doing when she posted the stories to her 11 million followers, the Bridesmaids star said.
"I don't classify it as an attack, I classify it as telling the truth," she told the court.
While Justice Raper noted her testimony could be self-serving at times, she accepted Wilson's evidence about the complaint made to her.
By contrast, the judge found MacInnes was a sometimes combative witness who had changed her story about the bath incident several times.
The young actor had walked back her complaint to Wilson a day later, partially because she was concerned she was losing control of the situation, Justice Raper determined.
MacInnes had received a lead role in a stage production and a six-figure record salary linked to Ms Ghost, the court was told.
The young actor was ordered to pay Wilson's costs.
MacInnes has been contacted for comment.
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