Armed police are on patrol at the entrance and extra security staff are on duty.
Everyone entering the courthouse has been required to removed their footwear for security screening - which is not usually part of the entry protocol.
Tarrant's lawyers, Auckland-based team Shane Tait and Jonathan Hudson, arrived at the courthouse just before 9.30am.
Family members of victims have also been seen arriving at court.
Some have told the Herald they have no interest in the court process or the accused.
But others want to be part of the judicial journey and will attend court when they can, and a number will be called as witnesses.
The trial for the 28-year-old Australian national - which could take six to 12 weeks - had been scheduled to begin on May 4 next year.
However, last month Justice Cameron Mander ruled the trial date be changed to June 2 due to the clashes with the Islamic holy month of Ramadan.
The accused will appear before Justice Mander again today via audio visual link from Auckland Prison.
His lawyers are expected to argue that his trial should be moved out of the city where the alleged mass murder took place.
At this stage it is set down for the High Court at Christchurch.
A transfer to another city would be permitted if the judge "is satisfied that it is in the interests of justice that the proceeding be heard at that other place or sitting", according to the Criminal Procedure Act.
