The appointment ends a four-month hunt for an editor after Greg Gutfeld left the magazine in March.
Harbinson will need to pull Maxim up the ABC rankings as a matter of urgency. The title was recently overtaken by IPC Media's Loaded and is now the sixth-biggest men's monthly. Its circulation of 190,438 is 300,000 short of the market-leader, FHM.
The monthly sector is struggling against IPC's Nuts and Emap's Zoo. Nuts sells more than 300,000 copies per week, Zoo more than 250,000.
Before his role at Nuts, Harbinson was the editor-in- chief at Haymarket's Customer Magazines division. He has also worked as a freelance features writer on The Sun and on Loaded.
Nuts has promoted Hans Seeberg, previously the associate editor for news and sport, to deputy editor.