The £185 million development, close to the port in the city of Nagoya, is expected to employ around 1,000 people.
Nick Varney, Merlin's chief executive, said: "The park will make a significant contribution to the growth of the Merlin group from opening in the second quarter of 2017, as well as supporting our continued geographic diversification.
"Long term, we continue to believe that there is significant opportunity for the Legoland brand, with the potential for up to 20 parks across the world and we remain committed to our target of opening a new park every two to three years."
Merlin said there is an estimated catchment area of 20 million people for the development. While the initial work will focus on the theme park there is additional room for extensions and themed accommodation.
The most recently opened Legoland parks were in Florida in 2011 and Malaysia the following year with a Dubai one to open in 2016.
Merlin also has Madame Tussauds, Alton Towers and the London Eye in its portfolio.
In Scotland Merlin operates Sea Life centres at Loch Lomond and Oban as well as the Edinburgh Dungeon.