Tarrant did not apply for bail and he was remanded to appear again before the court on April 5.
Earlier on Saturday morning, New Zealand Prime Minister Jacinda Ardern confirmed the gunman had obtained a Category A gun licence in November and "under that, he was able to acquire the guns that he held".
Ms Ardern said she would be seeking to change the laws that allowed the shooter access to these weapons.
"I can tell you one thing right now, our gun laws will change. There have been attempts to change our laws in 2005, 2012 and after an inquiry in 2017. Now is the time for change," Ms Ardern told reporters in Wellington.
She said the gunman used two semi-automatic weapons, two shotguns and a lever-action firearm during the attack, allowing him to shoot a rapid succession of rounds.
Australian police say the family of the suspect in the New Zealand mosque shootings is helping in their investigation.
NSW Police Commissioner Mick Fuller said Tarrant's family was from the northern NSW town of Grafton. He said the family contacted police after seeing media reports of the shootings on Friday. Mr Fuller said Tarrant spent little time in Australia in the past four years.
A senior Turkish official, who asked not to be named, said Tarrant travelled to Turkey multiple times and spent an "extended period of time in the country''. He said the suspect may have also travelled to Europe, Asia and Africa.
The names and faces of those killed, injured or still missing from the attack have begun to emerge.
Haji-Daoud Nabi, a 71-year-old man of Afghani origin, is among the dead.
His son, Omar Nabi, believes his father was shot as he tried to shield another person from the bullets.
"I got told by my best friend's father ... that he leapt on somebody else to save their life," Mr Nabi has told Stuff.co.nz.
"He jumped in the firing line to save somebody else's life and he has passed away... Just helping people is his main thing. It makes me feel like he wanted other people to live."
Dozens of others are still missing as officials work to confirm the identity of those killed.
The family of Farhaj Ahsan have not heard from him since the shooting.
Originally from the Indian city of Hyderabad, he is believed to have been attending Friday prayer at the time of the shooting.
Several of the victims were from countries in the Middle East and south Asia.
Bangladesh's honorary consul in Auckland, Shafiqur Rahman Bhuiyan, said three Bangladeshis were among those killed and four or five others were wounded, including two left in critical condition.
The Foreign Ministry of Jordan has confirmed that two of their nationals were among those killed.
One of Friday's massacres was live-streamed on the internet by the alleged attacker.
Tarrant, who lived and worked for some times in Grafton in NSW, filmed the attack using a headcam.
He described himself in a chilling 74-page manifesto as “just an ordinary white man, 28 years old”.
A security analyst described the document as “straight out of the white supremacist playbook”.
The manifesto said the attack was revenge for the "invaders in European lands" and "we must ensure the existence of our people, and a future for white children”.
He also wrote that he began planning the attack “roughly two years in advance”, and chose the final location three months prior to the attack because it was a "target rich" as any location.
On Friday night, New Zealand Police Commissioner Mike Bush said the death toll had risen to 49.
Tarrant allegedly live-streamed himself arriving at the scene by car, carrying out the shooting and then driving off in a car. Police apprehended a car he was travelling in shortly after the attacks.
Mr Bush confirmed three others were also arrested, and "a number of firearms" were recovered from the scene of both attacks.
“Three other people were apprehended - we believe one of those persons, who was armed, who was at the scene, may have had nothing to do with this incident," he said.
“The two other people that have been apprehended, again in possession of firearms in the general environment, we are working through to understand what their involvement is.”
Ms Ardern confirmed one of the arrested suspects was Australian-born and had extreme views. It was her understanding he was not on watch lists.
“At this stage the government has no reason to believe there are any other suspects,” she said.
Ms Ardern said her country had experienced one of its darkest days. “It is clear that this can now only be described as a terrorist attack," she said.
Ms Ardern said the attack appeared to have been "well-planned", with two bombs attached to cars, which were defused by police.
Ms Ardern said the attacker had extremist views and had no place in New Zealand, "and in fact have no place in the world".
"We were not chosen for this act of violence because we condone racism, because we are an enclave for extremism. We were chosen for the very fact that we are none of those things."
Prime Minister Scott Morrison confirmed one of the suspects taken into custody was Australian, describing the shootings as a “vicious, murderous” act of “right-wing” terror.
Tarrant filmed himself for 16 minutes as he allegedly sprayed victims with bullets during Friday prayers at the Masjid Al Noor mosque.
Twitter has shut down a user account in Brenton Tarrant’s name. It was not immediately clear whether Tarrant was involved in far-right neo-Nazi groups in Australia.
Tarrant, who attended Grafton High School, was dedicated to fitness and ran free athletic programs for children, former employer Tracey Gray said.
Ms Gray, the owner of Big River Gym in Grafton, said Tarrant worked at the gym about five or six years ago and "showed a lot of dedication to his own training" before obtaining personal training qualifications.
She said he left Grafton to travel the world. He reportedly had a sizeable inheritance after his father's death in 2011.
"I think something's really happened in this person's travels... he never showed any extremcies in conversations I had with him," she said.
"I'm almost trying to convince myself 'no' [that it's not him]. I have family in Christchurch and I can't get hold of them."
The shooters' rifles had "Alexandre Bissonette" and "Luca Traini" written on them - the names of mosque shooters in Italy and Canada.
Among the victims of the massacre was a four-year-old boy who was reportedly in a critical condition.
Farhaan Farheez was in the Linwood Mosque praying with about 100 others when the shooting started.
"I didn't know what a gun sounded like. It is customary when we are praying not to pay attention to the outside world,” he told Stuff.co.nz. “Gunshots kept happening and people kept praying.
"I saw two females and four or five males dead and the rest were severe casualties ... The whole mosque was filled with blood and dead bodies. It was like a battlefield."
The city immediately went into lockdown with police urging residents to stay indoors.
“We ask all mosques nationally to shut their doors,” New Zealand Police tweeted.
The Civil Aviation Authority declared the city of Christchurch a controlled air space and a crisis meeting of national security agencies was held in Wellington.
Mohan Ibrahim was one of 200 people in Masjid Al Noor mosque when he heard shots being fired.
"At first we thought it was an electric shock but then all these people started running,” he told the New Zealand Herald.
A man, who would not give his name, said he was praying in the Masjid Al Noor mosque when he heard the shooting start. He managed to escape, but outside saw his wife lying dead on the footpath.
"My wife is dead," he said, wailing. He was supported by other Muslim men who prayed for him.
Another man said he saw children being shot.
New Zealand’s last mass shooting was the 1990 Aramoana massacre, in which 13 people died as well as the killer David Gray.
Muslims Australia said the massacre was “a product of the ever-increasing Islamophobia and marginalisation of Muslims. (It) is a reminder to all concerned, including political leaders and media commentators, of the horrific consequences that an atmosphere of hate and division can lead to,” it said in a statement.
The Department of Foreign Affairs was working with New Zealand authorities to determine whether any Australians have been killed in the attack.
With AAP and Stuff.co.nz