The service, led by the Reverend Canon Katie Lawrence, will be open to the public.
That date of the service marks a month on from the Loafers Lodge fire.
The Service of Remembrance is being jointly organised by the Cathedral, the Wellington City Mission and the Office of the Mayor.
Watch the livestream of the service
Mayor Tory Whanau says: “This is an opportunity to come together and share the grief we’ve felt over the past few weeks as we remember those who lost their lives and homes.
Wellington City Missioner Murray Edridge says "The Service of Remembrance will enable us all to acknowledge the extent of this tragedy, to pay tribute to those that have come to help, and to demonstrate our collective aroha and manākitanga for those impacted by this terrible event."