Most stores have been barred from opening until 1pm, but the extended ban will keep retailers closed all day from 2025.
Premier Chris Minns said the inconvenience for shoppers would be a small price to pay to ensure Anzac Day remained an important commemorative date on the state calendar.
"We believe there's been a creeping commercialism of Anzac Day over a long period of time to the detriment of the importance of the day," he told reporters on Wednesday.
"There's many things that divide our communities in NSW and Australia, and the truth of the matter is Anzac Day is Australia's national day."
Retail trading restrictions vary across Australian states and territories, with only Western Australia having a total ban on Anzac Day shopping.
Victoria and Queensland allow trading from 1pm, while the ACT and the Northern Territory have no restrictions.
RSL NSW president Mick Bainbridge said the decision would allow veterans and their families to attend commemorations together.
President of RSL NSW Mick Bainbridge believes the change will protect the sanctity of Anzac Day. (Bianca De Marchi/AAP PHOTOS)
"It's a great way to ensure we protect the sanctity of Anzac Day, our most important veterans' day," he said.
Only businesses like cafes, restaurants, and chemists will get the tick in NSW - a move that the retail workers union the SDA says is supported by its members.
"It's not much to ask for retail workers to give up half a day of penalty rates, or for the community to give up half a day of shopping, when ... veterans have given up so much for all of us," NSW branch secretary Bernie Smith said.
But the nation's peak retail body said the change would impact workers unnecessarily, while also making it harder for people to shop for food in regional and remote areas.
"Changing this legislation will not change the way Australians come together on this important day," Australian Retailers Association chief Paul Zahra said.
It's hoped more people will commemorate veterans on Anzac day if shops stay closed. (Dean Lewins/AAP PHOTOS)
"Many workers are relying on public holiday rates to make ends meet during this incredibly challenging economic period."
Mr Minns defended the continuation of commercial sporting events on Anzac Day, such as the long-standing NRL match between the Sydney Roosters and St George Illawarra.
"We don't want our Anzac Day to be a solitary day," he said.
Opposition Leader Mark Speakman backed the extended trading ban, which he said ensured that veterans were properly honoured.
"It's a day of national significance and we must give everyone the chance to take part in commemorative services," he said.
Anzac Day is marked by dawn and sunset services, veteran marches and wreath-laying ceremonies. (Dean Lewins/AAP PHOTOS)
The premier also announced that $2 million would be spent to build the state's first major memorial for veterans of the Iraq and Afghanistan military campaigns.
Anzac Day marks the anniversary of the first major military action involving Australian and New Zealand forces during World War I.
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