The senator is fighting a claim by Central Land Council chief executive Lesley Turner that she defamed him in a July 2024 release.
Mr Turner said the release falsely reported a no-confidence motion had been moved against him by council delegates.
A hearing of the case began on Monday in the Federal Court in Darwin before Justice Michael Wheelahan.
The Northern Territory senator's release implied Mr Turner had "behaved so unprofessionally that it warranted his dismissal" and was "unfit to continue to occupy the role of CEO", according to his claim.
He and senator Nampijinpa Price sat on opposite sides of the public gallery on Monday, quietly listening to proceedings.
High-profile defamation lawyer Sue Chrysanthou SC, acting for the land council boss, said senator Nampijinpa Price and her staff had "ploughed ahead" with a defamatory media statement and failed to confirm the facts.
She said at issue was an alleged "coup" and what happened at a land council delegates' meeting in July 2025.
The barrister said Gavin Morris, then a headmaster at an Aboriginal school in Alice Springs, was one of the senator's trusted sources and had been an "intermeddler" in the whole affair because he wanted her client's job.
On Friday, the former Yipirinya School principal was found guilty in Alice Springs Local Court of assaulting four students in 2023, including putting them in choke holds and painfully twisting their ears.
He allegedly helped draft a media release for CLC chair Matthew Palmer saying delegates had voted on a no-confidence motion against Mr Turner.
The move came as Mr Turner and Mr Palmer were clashing over land rights issues.
The Palmer release said the "majority of Central Land Council members showed their support for the dismissal of the CEO due to unprofessional conduct".
The assertions were published by the NT News in an article titled "No confidence motion against Lesley Turner defeated".
The newspaper later pulled the article and issued an apology.
Ms Chrysanthou said Dr Morris had approached senator Nampijinpa Price about Mr Palmer's "plan for a coup" that included the removal of Mr Turner as CEO.
Senator Nampijinpa Price and her staff failed to question inconsistencies in the Palmer press release or confirm matters with sources, but went ahead with their own release that defamed her client, the barrister said.Â
When it became clear there was no vote of no confidence, the senator refused to accept that publicly and her "failure to act increased my client's hurt", she said.
"To this day Senator Price has never publicly admitted that what she said was wrong ... she's never made an apology for it," Ms Chrysanthou said.
"The senator ploughed ahead and gave the thumbs up for her staff to publish the press release.
"Instead of checking what happened, she didn't care what was true."
Ms Chrysanthou said the senator had her own agenda and "trampled on my client's reputation".
She noted the senator had removed a substantial truth defence to the defamation action in March without an accompanying apology.
The senator is instead seeking to rely on a defence of qualified privilege, saying her conduct in publishing the media release was "reasonable in the circumstances".
In an amended defence filed to the court she denies Mr Turner "suffered any hurt or that any such hurt has been aggravated by the conduct of Senator Price".
The senator has reportedly claimed the defamation bid could cost her a Senate seat if she was forced to declare bankruptcy.
The defamation hearing has been set down for seven days.
In September, Senator Nampijinpa Price was dropped from the shadow ministry for refusing to support Opposition Leader Sussan Ley and failing to apologise for controversial comments about Indian migrants.
