The parent company of KIIS and GOLD FM revealed the Henderson lawsuit on Tuesday, saying she was alleging in the Federal Court she was wrongly dismissed after complaining about longtime co-host Kyle Sandilands.
Henderson had filed a complaint letter in early March to an ARN subsidiary, saying she could not continue to work with her co-star of more than 20 years.
The letter came after Sandilands - who is also suing over his later dumping - mocked her on air on February 20 for her fascination with horoscopes in a discussion about disgraced former prince Andrew Mountbatten Windsor, accusing her of being "off with the fairies".
She made psychosocial health and safety and bullying complaints about Sandilands' treatment of her both during and before the on-air bust-up, ARN said in a statement to the ASX on Tuesday.
Henderson's contract was terminated after she issued the complaint letter, which she alleges was a breach of workplace protections and the terms of her contract, ARN said.
The radio star also claimed a previous market statement by ARN included misleading and deceptive statements under consumer law, the statement says.
She is claiming at least $82.25 million in compensation plus interest, legal costs and for ARN to face a court fine.
ARN, which has a market value of $90 million, said it disputes the claims and intends to fight them.
The announcement of another costly court battle is more bad news for the struggling radio company, which popped most of its eggs in the Kyle and Jackie O Show basket in late 2023, signing the stars to 10-year, $100 million contracts.
Instead, ARN is facing payouts totalling more than $150 million should it lose the cases.
The other half of the former top-rating morning show, Sandilands, appeared in court on Friday after he was suspended on March 3 and issued a breach notice for serious misconduct, which he denies.
Shares in the company, which also operates the GOLD and iHeart brands in Australia, have fallen at least 66 per cent since the 10-year deal was signed in November 2023.
The company shed 3.4 per cent in early trade on Tuesday to hit 28 cents.
Sandilands on Friday told reporters he regretted his comments to Henderson, while arguing it did not differ from his conduct over 25 years.
"We've had blow-ups before ... we just get over it, usually. So I think this has all turned into quite a circus," he said.Â
The Kyle and Jackie O Show was a consistent ratings juggernaut in Sydney but had failed to gain much traction in its expansion to Melbourne and Brisbane.