Amid tight security, Prime Minister Jacinda Ardern will join mourners near the Al-Noor mosque, one of the two places of worship targeted in last Friday's shootings.
Later a mass burial will take place for many of the victims.
Fifty people were killed and dozens more wounded in the attacks.
Australian Brenton Tarrant, a self-proclaimed white supremacist, has been charged with one murder and is expected to face further charges.
On Thursday Ms Ardern announced a ban on all types of semi-automatic weapons.
Thousands are expected to gather in Hagley Park, near the Al-Noor mosque, to mark Friday's national day of reflection for the victims.
The Muslim call to prayer, or adhan, will be broadcast on national television and radio at 13:30 (00:30 GMT) and be followed by the two-minute silence.
"We are so happy that this prayer will be broadcast to the entire world so that everyone can be part of it," said Mustafa Farouk, president of the Federation of Islamic Associations of New Zealand.
Many mosques across the country are expected to open their doors to visitors and human chains will be formed outside some in symbolic acts of protection and solidarity.