About $2.5 million has been spent on the Sofitel Auckland Viaduct Harbour since the world's biggest hotel operator took over running the former Westin.
Wouter de Graaf, Sofitel area general manager, said an upgrade had been under way since Accor began managing the hotel on the corner of Halsey St and Viaduct Harbour Ave.
Sofitel moved in last year and a lobby refurbishment is due to be finished at the end of this month.
The new So Spa is being built and that will offer seven private treatment rooms, he said.
A redesign of the restaurant, Lava Dining, is also due to be finished by the end of May, de Graaf said.