Australian Brenton Tarrant is likely to be jailed for life for the rampage.
Tarrant pleaded guilty in March and was convicted of 51 murders, 40 attempted murders and one charge of terrorism.
He is expected to appear in court for a four-day hearing at which survivors and victims' family members will speak.
The hearing will take place at the courthouse in Christchurch, the city where Tarrant carried out the attacks in March 2019. The first session is due to begin on Monday at 10:00 (22:00 GMT Sunday).
