Kelly Tarlton's British owners are spending $5.5 million to expand the aquarium's viewing space and introduce new features.
The Auckland waterfront attraction's general manager, James Thomas, said the upgrade had been long overdue, with the last major improvement to the aquarium taking place in 2006.
British-based Merlin Entertainment Group took over the business in March last year.
"We have been talking about the redevelopment ... for a number of years, and Merlin were aware of this when they came on board," said Thomas.
Merlin owns a variety of tourist attractions including the London Eye, the Madame Tussauds chains and the Dubai Aquarium.