Justice David O'Callaghan delivered his judgment in the Federal Court on Thursday following a three-and-a-half-week trial in September.
Mrs Deeming alleged Mr Pesutto defamed her by suggesting or implying she was a Nazi or Nazi sympathiser following a Let Women Speak rally in Melbourne in March 2023, a claim he denied.
Moira Deeming was supported by her husband and a group of women in court. (Joel Carrett/AAP PHOTOS)
The trans-critical event, which Mrs Deeming addressed and helped organise, was attended by men in black who performed the Nazi salute on the steps of state parliament.
The now-independent MP told the court those men had nothing to do with her rally.
Justice O'Callaghan found Mr Pesutto did defame Mrs Deeming in a media release, two radio interviews, a press conference and in a party expulsion motion.
Mr Pesutto implied she was unfit to be in the parliamentary Liberal Party because of her associations with Nazis, the judge ruled.
He ordered that $300,000 in damages be awarded to Mrs Deeming.
Mr Pesutto was not in court to hear the decision, while Mrs Deeming was supported by her husband and a group of women.
The group cheered after the judge left the bench, while Mrs Deeming's husband gave her a hug.