Prime Minister Jacinda Ardern joined thousands of mourners near the Al-Noor mosque, one of two places of worship targeted in last Friday’s shootings.
Imam Gamal Fouda, who led the prayers, said: “We are broken-hearted, but we are not broken.”
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.
What is happening on Friday?
Thousands of people have gathered 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, was broadcast on national television and radio at 13:30 (00:30 GMT) and was followed by a two-minute silence.
In an address beforehand, Ms Ardern said: “New Zealand mourns with you, we are one.”
“According to the Prophet Muhammad… the believers in their mutual kindness, compassion and sympathy are just like one body. When any part of the body suffers, the whole body feels pain.”
Victims of the Christchurch shootings
The Imam of Al-Noor mosque, Gamal Fouda, was there when the attack happened and said the gunman “broke the hearts of millions around the world”.
“Today, from the same place, I look out and I see the love and compassion,” he said.
“We are alive, we are together, we are determined to not let anyone divide us.”
One observer, John Clark, said the message was profound: “People will be rethinking how they react, how they think, and how they speak sometimes – it’s penetrated to that level of society.
“We like to think that we’re a liberal community, but we know that there are dark parts,” said Mr Clark, 72. “It will positively affect New Zealand and maybe we’ll have even more to offer the world.”
Many mosques across the country are opening their doors to visitors, and human chains will be formed outside some in symbolic acts of protection and support.
A mass funeral is being held for 30 of the dead, including the youngest victim Mucaad Ibrahim, aged three , who was killed at the Al-Noor mosque.