The service is being held on a Saturday to give friends of the church "every possibility'' to attend and say farewell, church officials say.
Parish spokesman Bob Avis said the church once attracted hundreds of people to services, but attendance numbers had dwindled to about 70, many parishioners unable to attend due to age-related or health issues.
The church was simply too expensive to maintain and there was no way to generate an income, he said.
In September last year, the congregation voted unanimously to dissolve as a group.
Ownership and responsibility of the church that had served its community for 135 years would be transferred to the Southern Presbytery and Synod of Otago and Southland.
Remaining parishioners were expected to join either the local St. Paul's or Waitaki (Eveline) congregations, Mr Avis said.
It is the second Oamaru church to close this year.
The Oamaru Union Parish, formed in 1970, had its last service on January 24.
Mr Avis said the congregation was upset about splitting up.
"Obviously there's a sadness. Many of our parishioners were here since they were children. They were baptised here. They've been through Sunday School here.''
But there was an understanding among many the closure was inevitable given changes in society.
"There's a move away from the established churches. Formal worship, the way we do it, doesn't appeal to many people these days and our congregation has grown smaller. We've tried to get more people to come, but we've had very little response.''
He knew his parish was not the only one facing closure, and said churches all needed to have an inward look at how and what they were delivering.
"Families don't see God as part of their life. I think they see us as irrelevant. They want to call on God only in emergencies, like firefighters.
"Sunday is not the day it used to be and I think the church has got to adapt to the new society its got itself. Having every service on a Sunday is a thing of the past. Services should be happening any day.''
The service will start at the church at 2pm tomorrow.
