Tarrant, a 29-year-old Australian, had previously pleaded not guilty to all charges
A suspected white supremacist accused of killing 51 Muslim worshippers in New Zealand's worst mass shooting changed his plea to guilty in a surprise move on March 26.
Brenton Tarrant, who appeared by video link, admitted to 51 charges of murder, 40 charges of attempted murder and one charge of committing a terrorist act in a hastily called Christchurch High Court hearing.
"He has been convicted of each and every one of those charges," presiding judge Justice Cameron Mander said in minutes of the hearing released by the court.
"The entry of guilty pleas represents a very significant step towards bringing finality to this criminal proceeding," Justice Mander said.
Tarrant has been in police custody since March 15, 2019, when he was arrested and accused of using semi-automatic weapons to target Muslims attending Friday prayers at two mosques in Christchurch. The attack was streamed live on Facebook.
Tarrant, a 29-year-old Australian, had previously pleaded not guilty to all charges.
Justice Mander said there was now no need for the six week trial that was previously due to begin on June 2.
The court will now sentence Tarrant on all 92 charges, but did not provide a date for that sentencing. Tarrant was remanded in custody until May 1.
Due to a nationwide lockdown in place for the coronavirus outbreak, Thursday's court hearing took place with just 17 people in the courtroom, which included minimal staff, lawyers and some local media. An Iman for each of the two mosques attacked were also allowed to attend the hearing.
New Zealand announced a nationwide lockdown starting on Thursday, to combat the spread of coronavirus.
The court placed a one-hour embargo on reporting the news in order to inform family members and victims about what had taken place before it was made public.
"The guilty plea today will provide some relief to the many people whose lives were shattered by what happened on March 15," Prime Minister Jacinda Ardern said in a statement.
"These guilty pleas and conviction bring accountability for what happened and also save the families who lost loved ones, those who were injured, and other witnesses, the ordeal of a trial," she said.