She replaces John Luxton, who stepped down as DairyNZ chairman and retired at today's annual meeting.
Two sitting board members- Ben Allomes and Michael Spaans were re-elected for anther term.
Cook has served as an associate director of DairyNZ; she was the 2006 NZ Sharemilker of the Year and was a finalist in the NZ Dairy Woman of the year award this year.
She has 30 years dairy farming experience in Waikato and Southland.
Meanwhile DairyNZ will appoint a new chairman at a board meeting early next month.
Barry Harris will act as chairman until the new leader is appointed.
Former Fonterra director Jim van der Poel is the frontrunner for the post.
