Kerry Stokes' Seven Network Ltd has taken a $100 million stake in James Packer's Consolidated Media Holdings Ltd (CMH).
Seven, of which Mr Stokes owns 44.9 per cent, is believed to have acquired a 4.82 per cent shareholding in CMH over the last few months, the Australian Financial Review reported.
Seven and CMH did not return calls by AAP on Friday.
Based on CMH's closing share price on Thursday of $3.16, Seven's holding would be worth around $100 million.
Seven closed down three cents to $8.07 on Friday.
CMH lost three cents to close at $3.13.
The reported deal would give Seven an indirect investment in its rival Nine Network and Foxtel, Australia's monopoly metropolitan pay TV business.
It could also be a move by Mr Stokes, Seven's chairman, to build a blocking stake to prevent any rivals taking over CMH.
CMH, which is 38.4 per cent owned by Mr Packer, has a 25 per cent interest in PBL Media - which owns the Nine Network, magazine business ACP and a 50 per cent interest in ninemsn and other websites.
It also owns a quarter stake in Foxtel, half of the Premier Media Group, which owns Fox Sports, and 27 per cent of employment website company Seek Ltd.
Seven's move comes several months after parties led by tycoons Mr Packer and Lachlan Murdoch attempted to privatise CMH in a $3.3 billion deal, which collapsed after a major financial backer withdrew its support.
Seven last year restructured its media assets, selling 52.3 per cent of its TV, magazine and internet assets for $3.2 billion to private equity firm Kohlberg Kravis Roberts & Co (KKR).
Deutsche Bank media analyst Andrew Anagnostellis said there was little that could be said about the deal as the company was not required to disclose a holding below five per cent under the rules of the Australian stock exchange.
"There has been no disclosure and the company is not saying anything," Mr Anagnostellis said.
"All we know is Seven has a lot of cash."
As of February, Seven had a $1.7 billion "war chest" flowing from the proceeds of the sale to KKR and $800 million more in listed securities.
Seven owns a 19.4 per cent stake in West Australian Newspapers Holdings Ltd (WAN), 100 per cent of wireless broadband company Unwired Ltd and also owns stakes in internet telephony company Engin Ltd and environmental services company GRD Ltd.