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.
Rooms have been upgraded with new framed MyBed units, personal espresso machines, LCD televisions and Bose sound systems in suites.
The hotel was well placed to take advantage of the Wynyard Quarter expansion where about $1 billion of private investment is being sought, he said.
The property became a Sofitel last February and about 50,000 people had stayed there since then, de Graaf said.
The hotel is the second in New Zealand for Sofitel, which also operates in Queenstown.
A third site was planned for 2014 when a new Wellington property would open, de Graaf said.
Auckland's Sofitel is owned by multimillionaire low-profile Auckland family the Pandeys who are based on Queen St but have hotels around the world.