The roof fire occurred in August 2020 and left the building with a hole in the roof and a water-damaged floor.
The Very Rev Dr Tony Curtis, dean of the cathedral, said the repairs in the main hall were almost complete and the scaffolding would be removed for the service this Sunday.
However, the cathedral was undergoing more than just basic repairs, as the fire created an opportunity to address accessibility issues and cultural requirements within the building, he said.
It claimed to be a church for everybody, but at present there were no disabled toilets, lifts, baby changing rooms or gender-neutral rest rooms.
"A church should hold up its people."
That meant all the people of Otago, not just those in the architect’s mind when it was built in 1919.
The hall underneath was "completely flooded out", but the church took the chance to redevelop it and create a modern community space which could be used for charity events, art shows, gigs and more.
A church was meant to celebrate all of God’s creativity, not just that traditionally seen in worship, he said.
A new sanctuary would be created that acknowledged and celebrated the Maori, Pasifika and Pakeha elements of the church.
One of the most recent improvements was a new organ console, which was electronically connected to the pipes and could be moved around.
The upgrade work would continue for another year or two, but the removal of the scaffold felt like "things are getting back to normal", he said.
Although it was likely the cause of the fire would never be known for certain, it was probably caused by faulty wiring in the ceiling installed about 50 years ago.
After the blaze worship was held at the nearby St Joseph’s Cathedral, which the Catholic diocese had allowed the church to use.
People had to "tiptoe" around cables and different services had to slowly relocate around the building as work progressed.
A large white sheet was hung up to stop dust spreading from the work area to the rest of the cathedral.
Most of the damage done by the fire was covered by insurance, but the cathedral had used funds and worked with community groups to further the improvements.
The final touches on the outside of the building would begin early next month and the external scaffolding would hopefully be down for Christmas, Dr Curtis said.
