The doors to the mall opened at around 7.50am. There were queues of people outside the Huffer store, outside the mall, from 4am, ahead of the store and shopping mall's official opening at 9am.
Thousands of people watched from all levels of the shopping centre as Western Springs College performed a cultural performance, waiata and haka, which had the floor of the mall shaking at one point, to mark the opening.
A ribbon-cutting ceremony was held outside department store Farmers just before 8am.
Scentre Group expects tens of thousands of shoppers to visit the shopping centre over the weekend. The Australian mall operator is holding a series of events and giveaways throughout the day.
A number of retailers are marking the occasion, offering discounts and freebies.
Chemist Warehouse was this morning giving away water bottles, another retailer was giving away flowers and Australian streetwear retailer Dangerfield was offering 20 per cent discounts on some purchases today and over the weekend.
Other retailers, such as Huffer, are giving away free coffee.
The entire Westfield Newmarket site is expected to be open in time for Christmas.
Australian furniture retailer Coco Republic opened its first New Zealand store in the mall today. It is joined by discount pharmacy chain Chemist Warehouse, Under Armour, Kathmandu, clothing retailer Dangerfield, Huffer, EB Games, Amore Gelato, Spark, Bras N Things and the Cosmetic Clinic, among others.
Before Christmas, Westfield Newmarket plans to have all 230 shops open, as well as an alfresco rooftop dining and entertainment precinct, including a gym and Event cinema. The centre will house a Peruvian-style restaurant, Inca, arcade bar Archie Brothers Cirque Electriq, and 10 other hospitality outlets, including White + Wong's, Sardine Cocktail Bar and Something & Social.
Other retailers set to open in the mall include New Zealand's first Lego store, department store David Jones on the adjacent site, and clothing brands General Pants Co, Aje, Camilla and Zimmerman.
Auckland shoppers Lucy Vanspall and Michaela Wray, who headed along to the opening of Westfield Newmarket this morning, said they were impressed by the new mall.
Wray said the first stage of the mall was "nice and open", and "very different" to the Westfield Newmarket she used to visit before the redevelopment.
The pair, originally from England and Northern Ireland, usually shop at Sylvia Park mall in Mt Wellington. They said it was too soon to say whether Westfield Newmarket would become their preferred shopping centre.
"I'm from Northern Ireland so this amazing compared to what we have," Wray said.
"Loads of the shops are closing down back home because of online shopping, it's actually kind of depressing. Shopping in New Zealand, I think, is better than at home," Vanspall told the Herald. "It's nice to see the shops still busy here."
Chelsea Smith, New Zealand area manager for Australian clothing retailer Dangerfield which today opened a store in the mall, said she wasn't expecting so many people to turnout for the opening.
"I feel like the projections and the way everybody is talking about [Westfield Newmarket] is that it is to hopefully rival Sylvia Park, which hopefully means this should be our top-performing store in the future. We definitely have high hopes," Smith said.
Dangerfield's Newmarket store was its first mall-based store in Auckland, she said.
Huffer co-founder and director Steve Dunstan, who was at the opening of the mall, said the clothing brand's Westfield Newmarket store would replace its Nuffield store located in Newmarket.
Dunstan said the first person waiting in line for the store to open had been waiting there since 4:30am. Around 200 people were waiting outside the shop ahead of its opening.
"To see the queues, it was pretty overwhelming to have that level of support," he said.
Huffer has ten stores in New Zealand, and has traded in Newmarket since August 2011.
"We've always said we're not a mall brand, but we have a street entrance and it looks like so many people are coming in off the street, which is really important to me," Dunstan said.
The fit-out budget for the Westfield Newmarket store was the most the brand had ever spent on a single store, Dunstan said. He would not share specific figures
"It's not about the bling that makes a store good, it's about how customers can engage with it. The biggest cost, to be honest, is the space - the lease and per sq m rate is higher in developments like this - to have space costs a lot of money."