The $700,000 upgrade of facilities at St Andrew's Church began late last year when the old hall was demolished.
The parish minister, the Rev Brian Walker, said the new building in George St would "wrap around" the existing church building.
Services have been held at the parish's Balmoral church in north Balclutha in recent months while building work continues at the central Balclutha site.
Mr Walker said final work was being completed on site and the official opening would take place on Sunday, July 26.
Instead of the usual Sunday morning service, an afternoon service, starting at 2pm, would be held that day.
Otago-Southland Presbyterian synod moderator Christine Hansen, of Cromwell, will officiate at the gathering, which will start in the church before moving through to the new hall, where a ribbon-cutting ceremony will be held.
The development's main feature is a multipurpose hall which should prove ideal for large crowds gathering for weddings and funerals.
The former hall was small.
Data-projec-tion connections would mean a funeral director could house overflowing crowds in the hall when the church was full and provide a direct visual and audio link to the main service next door.
These facilities would also allow conferences and other large-scale events to be held there, Mr Walker said.
The single-level building had been in the planning for more than two years and he said it was a good idea to incorporate new technology into the new building.
Meeting rooms, toilets and new headquarters for the South Otago Foodbank would also be incorporated.
Mr Walker said it was an exciting project, which was fully funded by the parish and external grants.
