Mihocek leaves the Magpies after eight seasons, while the Brisbane Lions have officially landed Essendon's star ruck Sam Draper.
A five-time leading goalkicker at the Magpies, Mihocek will bring valuable experience to a rebuilding Demons outfit led by new coach Stephen King.
Melbourne star Christian Petracca has already requested a trade to Gold Coast, while Clayton Oliver was spotted on a boat in Sydney Harbour with GWS coach Adam Kingsley and football boss Jason McCartney.
Mihocek played 159 games across eight seasons in black and white and kicked 47 goals as a key member of Collingwood's 2023 premiership.
The 32-year-old boasts a total of 267 career goals since making his debut for the Pies in 2018.
"Brody has played a key role within our football program over the past eight years, and we thank him for his contribution to the black and white," Magpies list manager Justin Leppitsch said in a club statement.
"We respect Brody's decision to pursue his free agency rights and explore opportunities at Melbourne.
"We wish him, his partner Polly and their son Arthur all the best for this next chapter.
"As a 2023 Premiership player, Brody will always be a Collingwood person."
Mihocek leaves Collingwood after teammate Jamie Elliott turned down interest from Gold Coast to re-sign for a further two years.
Meanwhile, back-to-back premiers Brisbane have snapped up Draper as an unrestricted free agent.
Draper played 78 games after spending nine years on Essendon's list.
The 27-year-old cited a troubled injury stretch at the Bombers as among his reasons for leaving the club.
Essendon have landed pick 20 as compensation for Draper departing, boosting the embattled club's draft hand further.
The Bombers, who could gain further picks and/or players if, as expected, they trade disgruntled captain Zach Merrett, already have five draft selections inside the top-30.
Meanwhile, Collingwood star Bobby Hill's bizarre 2025 has continued after gaining permission from the Magpies to play in an Indigenous Victorian football carnival.
Hill, the 2023 Norm Smith medallist, dealt with serious personal issues this year and was not considered to play in either of Collingwood's two finals.
Magpies coach Craig McRae left the door ajar for Hill to return if Collingwood won their preliminary final against the Lions and progressed to the decider.
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