Prime Minister Jacinda Ardern announced the event, to be held in Christchurch on Friday, two days after she attended prayers near one of the targeted mosques, Masjid al Noor.
"In the week since the unprecedented terror attack there has been an outpouring of grief and love in our country," she said.
"The service will be a chance to once again show that New Zealanders are compassionate, inclusive and diverse, and that we will protect those values."
It's hoped the service will be broadcast live to events in Auckland, Wellington and Dunedin.
'We will be united by love'
Christchurch Mayor Lianne Dalziel said the events of March 15 would not define the city but the aftermath would.
"We will not be divided by hatred, we will be united by love."
Foreign dignitaries descended on Christchurch along with Ms Ardern last Friday as the Muslim community returned to prayers outside Masjid al Noor, before it and Linwood Masjid had been handed back to the community.
The prime minister expects the same for the memorial.
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The royal family is understood to be sending a representative, rumoured to be Prince William who has visited the city several times, including after the 2011 earthquakes.
Jordan's Crown Prince arrived shortly after the mosque attacks on March 15, and visited Masjid al Noor on Saturday.
The Muslim community reclaimed the mosque with hugs and prayers a week and a day after the tragedy.
At first only a small group was permitted to pass through the cordon but once the barricades came down the lines grew, as grieving families and those who escaped with their lives came back.
They were joined by friends and strangers wanting to show solidarity and support.
More are set to return on Sunday night when a vigil is held for the dead and injured.
Among the injured are 25 who remain in hospital, four critical in intensive care.
New Zealand on edge
Life has largely returned to normal across the city and country, though the nation remains on edge.
A music festival in Wellington on Saturday night was partially evacuated by police after event security raised concerns about what was thought to be a far-right tattoo, but was not.
The armed police presence around the mosques is set to continue and it has been welcomed, including by Huzef Vohra who was inside the mosque and lost 80 per cent of his friends in the attack.
"If they could (stay), it's really better," he said.
The man charged with murder over the attack, 28-year-old Australian Brenton Tarrant has been transferred from Christchurch and is being monitored around the clock and has no access to television, radio, newspapers and no approved visitors.
Ardern says NZ cabinet agrees on tougher gun laws 'in principle'
He allegedly used two semi-automatic rifles legally bought with a licence.
From 3pm on Thursday such weapons became illegal under interim measures, until legislation is expected to be introduced by April 11.
Police have already received more than 1000 notifications from people wanting to hand in their now-banned weapons.
Additional reporting: AFP