NORTH Melbourne has acquired Melbourne midfielder Dom Tyson on Friday in a deal that has also seen ruckman Braydon Preuss join the Demons.

As part of the trade, the Demons will also receive a fourth-round pick (currently No.62) from the Kangaroos.

AFL.com.au first reported Melbourne's surprise interest in Preuss in August.

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It is understood the Roos initially baulked at the inclusion of Tyson in the deal, but when they missed out on West Coast free agent Andrew Gaff, they were more open to taking on the former Demon's significant salary. 

Tyson, 25, enjoyed a solid five seasons with Melbourne where he averaged more than 20 disposals per game in each season. He played the first two years of his career at GWS.

"Dom was a really important player for us for five years," Melbourne footy boss Josh Mahoney said.

"He was one of the first players to come to our club during this rebuild."

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Preuss, a 206cm ruckman, was stuck behind Todd Goldstein at North Melbourne, managing just eight games across four years. He is likely to deputise behind Max Gawn at Melbourne.

"We needed a backup ruckman and Braydon Preuss has shown at VFL level that he can play that," Mahoney said.

"Braydon has said to us he wants to learn under Max Gawn and our ruck coach Greg Stafford… Max is really excited by it."