Amazon sees New Zealand and Australia as one big market and is tipped to be just days away from launching operations across the Tasman.
"Amazon views Australia and New Zealand as the one market," says e-commerce adviser Hamish Conway, director of Sell Global. "They are absolutely after the New Zealand consumer.
"People have all got in their heads that [the launch] is about Australia, and the Australian market, but actually it may as well be Amazon.co.nz."
New Zealand businesses should see the launch - which is widely tipped to be this week - as an opportunity, Conway said.
"From a business point of view, you could be an Auckland business that sells products, lifting your products on Amazon.com.au, and sell to a person down in Dunedin who buys off the Amazon store, and you ship it from Auckland down to Dunedin, so the product never even goes to Australia - that type of transaction hasn't really been talked about," he said.
"Amazon will very quickly dominate. It will be the main e-commerce platform in New Zealand very quickly."
Conway said the breadth of catalogue available on Amazon would "eat Trade Me and Mighty Ape for lunch".
Bricks and mortar retailers would be safe - safer than e-commerce stores, he said.
"Brand-owned web stores will potentially, if they're not very good, [diminish]. Shoppers will go 'Oh, it's way easier on Amazon; it's fast, I get comparisons, I get low-cost or free shipping', so they really are up against a giant."
The majority of products sold on Amazon are through third-party sellers.
E-commerce stores that feel the pinch the most would be aggregation-type websites such as pharmacy and sporting goods websites, "where the website owner doesn't own any of the brands".
Last year 43 per cent of all online retail sales in the United States went through Amazon.
Food categories would be harder to list in to compared with clothing, homeware, sports equipment, outdoors and DIY products, Conway said.
He didn't think New Zealand retailers or businesses would feel the effect of Amazon's arrival immediately.
"It could happen very subtly and quietly.
"There will certainly be some fanfare, and I think New Zealanders will adopt Amazon faster than Australian consumers."
New Zealand's retail sector was in for a shake-up, he said.
"When people think Amazon, they think cheap prices but that's not so ... Retailers are going to have to really love the customers they do get and look after them - they'll have to provide an experience so people want to come in to the store."
Retailers such as The Warehouse, Briscoes, Rebel Sports, and those who sell smaller products easily shipped, will feel the impact of Amazon, Conway said.
"Within six months I think they'll start to notice a drift away."
Nick Grayston, chief executive of The Warehouse, said the company had been making changes to its operations.
"We've been making a number of changes for a while now, not necessarily in advance of Amazon's arrival, but more to defend our market share compared to many of our peers," he said.
"We've focused on leveraging our home advantage by transforming our bricks and mortar businesses and ensuring our retail fundamentals are sound, while also building compelling digital capabilities and channels for the future."
Business Mentor NZ retail mentor Kate Wright said Amazon Marketplace offered an opportunity for small businesses to reach a wider audience.
"The trick will be knowing which particular marketplace set-up is right for your business, learning the ins and outs of how to stay visible, and how to stand out from the competition in this 'new' ecosystem," Wright said.
Amazon will very quickly dominate. It will be the main e-commerce platform in New Zealand very quickly.
While Amazon offered another avenue for business, Wright said there were possible downsides such as third-party sellers getting hold of discounted or old stock that could end up listed without your control.
"The decision essentially comes down to how it fits within their current business model and desired future model. In terms of sheer scale and capability, anything you can do, Amazon can likely do better, faster and cheaper," Wright said.
"The most important consideration for small businesses that want to stick around and remain profitable in the long term is reputation so that should be factored into any decision-making process."
It is likely Amazon would build a warehouse in New Zealand within the next five years, Conway said. "They're not afraid to invest, and they like to dominate."
Amazon's upcoming arrival in Australia is said to be a soft launch offering online limited categories ahead of its Melbourne warehouse opening.
"In New Zealand, I don't think it's going to create any big dent in the retail market this side of Christmas. It will start to have an impact but it will be under the radar - single-digit percentage impact. But this time next year they'll be in full-flight."