Highbury's current non-executive chairman Simon Nethercoat is making way for MacKenzie immediately.
The current chief executive Mark Simpson was already due to step down on September 30. However, the arrival of MacKenzie means he will no longer be taking up the deputy chairman role.
A spokesman for Highbury said that Mike Frey, the current managing director of Highbury's entertainment division, is still due to take over from Simpson as chief executive.
The news follows a month of speculation about MacKenzie's motives for buying up Highbury shares. He built up his stake from the beginning of August but stopped before nearing the 30% level at which takeover rules mean he would have had to bid for the whole company.
MacKenzie acknowledged that Highbury is still facing financial problems.
"The company remains in a fragile state but at its heart are good titles and core profitability. I am hopeful we can build on this foundation," he said.
The role is MacKenzie's first since he left The Wireless Group in May after its acquisition by Ulster Television. He had failed in an attempt to take control of the radio company in a management buyout with private equity backing, but left with a sum believed to be in excess of £7m for his 6.4% stake and his severance package.
Highbury has been forced to sell off and close various magazines in a downturn following a strategy of expansion. It was almost sold to rival publisher Future earlier this year but the deal was blocked by competition worries and it instead sold 38 magazines to Future.
It still has 43 magazines, mainly in the computer, photography and craft sectors but also including lads' mag Front and film magazine Hotdog.
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