By the way, today's announcement doesn't mean that Japan hasn't been hunting whales all this time.
Japan will recommence industrial whaling in July 2019 after a 30-year absence "in line with Japan's basic policy of promoting sustainable use of aquatic living resources based on scientific evidence", he said.
In a notable shift, Japan also said it will no longer conduct controversial hunts in the Antarctic Ocean - where its fleet of whaling ships have killed 333 whales in each of the past two years, under the justification of performing whale research.
Leaving the IWC means Japanese whalers will be able to resume hunting in Japanese coastal waters of minke and other whales now protected by the IWC.
Astrid Fuchs, program manager for Whale and Dolphin Conservation told National Geographic Japan's decision could have global ramifications.
Ahead of the announcement, activist groups warned Japan against the withdrawal.
Japan has hunted whales for centuries but has subdued its catch following worldwide protests and diminishing demand for whale meat at home.
Around 200,000 tons of whale meat was consumed in Japan each year in the 1960s, but it has fallen sharply to around 5,000 tons in recent years, according to government data.
"Australia remains resolutely opposed to all forms of commercial and so-called "scientific" whaling", Foreign Minister Marise Payne and Environment Minister Melissa Price said in a statement.
Anti-Whaling protesters at South Bay, Kaikoura.
"This is the path of a pirate whaling nation, with a troubling disregard for global rule", she added.
Sam Annesley, Greenpeace Japan's executive director, said: "It's clear that the government is trying to sneak in this announcement at the end of year, away from the spotlight of worldwide media, but the world sees this for what it is".
"The declaration today is out of step with the global community, let alone the protection needed to safeguard the future of our oceans and these majestic creatures", worldwide conservationist group Greenpeace said.
The IWC in September again rejected Tokyo's request to resume commercial whaling.
The whale hunts will abide by worldwide laws and a quota calculated under a method adopted by the IWC.
"We ate whale meat in the old days but there are lots of other things to eat now", said a 75-year-old woman shopper.
"The Commission is the pre-eminent global body responsible for the conservation and management of whales and leads worldwide efforts to tackle the growing range of threats to whales globally, including by-catch, ship strikes, entanglement, noise and whaling".
Since then, Japan has repeatedly called for a resumption of commercial whaling of species whose numbers have recovered.
The ever-dwindling demand means an uncertain outlook for Japan's whaling.
Though the government has actively defended whaling, consumption of whale meat at home is on the decline.