The Ministry of Business, Innovation and Employment's quarterly international visitor survey also found visitor numbers fell 2 per cent last year.
TNZ said it had partnered with Air NZ and Emirates to bring 140 agents from the UK, Europe, North America and Mexico, and 300 from across the Tasman.
The travel agents will be escorted around the country - visiting spots like Hobbiton and Waitomo - and will participate in a day-long training workshop on how to sell New Zealand.
"The travel trade is an extremely valuable tool for engaging with potential visitors, and a well-informed agent is better equipped to promote and sell New Zealand," said TNZ spokesperson Justin Watson.
Bringing agents to New Zealand would have obvious pay-offs for the country, he said.
"It increases their destination and product knowledge which in turn serves to act as motivation for them.
"Agents will be more motivated and confident in promoting a product they know and have experienced for themselves."
Watson described bringing 440 agents to New Zealand as "an enormous logistical exercise".
Air New Zealand's Chris Myers said there was no better way to make sure trade partners were motivated and trained to sell New Zealand than inviting them to experience the country first-hand.
"The mega-famil is a great initiative that will help stimulate demand for holidays in New Zealand," he said.
The two overlapping events will span 10 days. Agents from the UK, Europe, North America and Mexico arrive from May 10 and those from Australia on May 15.