Garner joins the exhibition, events and live music venue from Wembley City, where he was head of commercial and property.
His new responsibilities will cover both events management and operations teams.
Alexandra Palace is still on the look out for a head of sales and a marketing manager to complete its new management team.
Voted number ten in Event magazine's Top 20 Venues poll, the venue recently hosted the star-studded Damilola Taylor Trust's Spirit of London Awards and Jay-Z's last UK concert.
A £300,000 investment has seen improvements to its West Hall floor and new bar areas added within the Great Hall, which now has an increased capacity of 10,250.
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