This is the last of 18 years his company Eventpro would manage the event, which under his watch has become the largest equestrian show in the Southern Hemisphere.
Last year Eventpro signed a joint venture with Australian-based business Equine Productions.
Mr Hansen leaves for Sydney next month, leaving son Andrew, current HOY manager, to manage the New Zealand arm of the merged companies.
HOY won't be managed by Eventpro, preferring to explore "new opportunities" after the company that has long-term rights to the show, Horse of the Year (Hawke's Bay) Ltd, announced last year it would consider tenders for the management contract.
HOY chairwoman Cynthia Bowers said Mr Hansen would leave a big pair of boots to fill.
Bringing the show to Hawke's Bay, from owner Equestrian Sport New Zealand, and growing it while retaining it in the region was a significant achievement, she said.
Mr Hansen left HOY "in a good place going forward".
"The challenge for us is going to be to find an event manager to take us to the end of the 2017 year and beyond. We are optimistic we are going to have some pretty good options."
Hawke's Bay has rights to the show for three 5-year terms, with the current term to be renewed after the 2017 show.
An area of recent growth has been seminars for equestrian event officials.
"People are flying in from all over the world to take these, to get our New Zealand and Australian officials' experience," Mr Hansen said.
One event again no longer on the HOY programme is showjumping's Holy Grail at Church Road Winery. The inaugural 2013 against-the-clock event was held days before HOY's official start but was cancelled last year because of a forecast cyclone, which bypassed the region.
"The top riders put so much emphasis on the Olympic Cup and the big classes at the show, so to bring them down two days earlier is very difficult," Mr Hansen said.
"The top riders didn't want to do it and we didn't want to put a lot of prizemoney in it because that took away from HOY.
"I personally think the Holy Grail-type concept at Church Road has a real future, but not two days before HOY."
With Equine Productions he is launching a new equestrian event in New South Wales, the Equine Lifestyle Festival.
"It will be the largest event in the Southern Hemisphere in November, bigger than this one."