She was found in 2024 to have racially vilified deputy Greens leader Mehreen Faruqi by telling her to "piss off back to Pakistan" in a tweet posted shortly after the death of Queen Elizabeth II.
In his Federal Court decision handed down in 2024, Justice Angus Stewart ruled it was "seriously offensive" and a "strong form of racism".
Senator Hanson launched an appeal against the finding, with her barrister arguing the remarks might not have been pleasant but they did not intimidate people of colour.
The appeal was dismissed by the Full Court of the Federal Court on Monday, nearly four years after the social media post that landed the firebrand politician in hot water.
It came in response to a post on X, formerly Twitter, from Senator Faruqi on the day of the Queen's death in which she offered her condolences to those who knew the monarch.
But she added she could not mourn the passing of the leader of a "racist empire built on stolen lives, land and wealth of colonised peoples".
In a heated retort, Senator Hanson said she was appalled and disgusted by the comments.
"When you immigrated to Australia you took every advantage of this country," she wrote.
"It's clear you're not happy, so pack your bags and piss off back to Pakistan."
The remark was the "ultimate racist slur", Senator Faruqi noted after her victory in the Federal Court two years ago.
The social media stoush isn't the only time the two politicians have clashed, with some of Senator Hanson's more eye-catching stunts in the Senate drawing her colleague's ire.
The Greens senator accused the right-winger of blatant racism and Islamophobia when the latter wore a burqa into parliament, just six days after the appeal hearing in November.
It was the second time Senator Hanson had pulled the burqa stunt.
The 72-year-old has recently come under fire since returning from a European trip, where she was seen holidaying in Italy with billionaire donor Gina Rinehart.
Senator Hanson also met with anti-immigration activist and convicted criminal Tommy Robinson and told a conservative conference Australia had been flooded with migrants.
Since returning, she has attracted criticism for describing domestic violence as a "two-way street" in comments she insists have been taken out of context.
A Roy Morgan poll published on Tuesday showed her anti-immigration party's primary vote dipped more than five percentage points to 22.5 per cent in the space of a week.
