Mayor Bryan Cadogan said it would be a time of ''reflection'' following the tragic deaths.
He said Balclutha residents had come together in ''solidary'' to support the local Muslim community in the aftermath of the shootings.
While the national day of mourning was scheduled for Friday - a request had been made by the Muslim community to hold something outside of business hours.
Mr Cadogan was asked to limit disruption to Silver Fern Farms as ''they do not want any further disruption to staff or the company.''
He said it would also be an opportunity to remember Mohamed Elmi who died in a crash near Palmerston while returning to his Balclutha home after visiting his Christchurch family affected by the attack.
''It is also a time to show our love and support of the local Muslim community as they come to terms with recent events.''
The service will be held at the Balclutha Town Hall, starting at 7pm. A large crowd was expected and
he encouraged people to arrive early.
The service will include music and a combined kapa haka from local pupils.
