The service is open to everyone, and will be attended by town councillors as well as representatives from community organisations. It will be jointly led by a range of ministers from Tavistock Area Christians Together (TACT).
The theme of the service will be the importance of serving others, and will highlight the role of volunteers.
An introduction to Tavistock Memory Café will be given at the service by June Wildman, and the preacher will be the Rev Mike Lapage, who will speak on the theme of 'service' in this Olympic year. Mr Lapage is a local retired priest, and one of the last remaining UK silver medalists of the London Olympics of 1948.
The Rev Michael Brierley, priest in charge of Tavistock, said: 'Mike is a wonderful and godly man. He is very modest about his Olympic achievements, and has had some amazing experiences this year while hiding his light under a bushel.
'I am very glad that he will be kindly sharing with us his thoughts on service from an Olympic perspective.'
The mayor warmly invites everyone to the service, which begins in St Eustachius' Church at 6pm, and finishes with refreshments in the town hall.