Clergy, parishioners and former parishioners from all over Otago and Southland attended the celebrations marking the centenary of the Catholic Church of Mary Immaculate and the Irish Martyrs.
The stone building on Sligo St was opened on April 18, 1909.
It was the second Catholic church built in the town.
Its orange-tiled roof and 20m belltower can be seen from State Highway 8, across Lake Dunstan.
A get-together was held in the church hall on Saturday and about 200 people took part in a centenary Mass at the church yesterday.
The Catholic Bishop of Dunedin, the Most Rev Colin Campbell, took the service, with the assistance of Fathers Mervyn McGettigan (Mosgiel), Michael Hishon (Milton), Brian Fenton (Wanaka), Brian Traynor (Waikiwi), Paul Mahoney (Cromwell), Brian Dougherty (Invercargill) and Monsignor Vince Walker, of Dunedin.
Bishop Campbell said an article on the church, published in the New Zealand Tablet, on April 22, 1909, declared it "far and away the handsomest building in Cromwell".
"We have been blessed by all the families and individuals involved in building up this parish, who have made it what it is," Bishop Campbell said.
"Our heartfelt thanks goes to God and all those people who are so faith-filled and remained loyal to their faith in difficult times."
The church was given its unusual name in an attempt to gain the support of the mainly Irish Catholic gold-miners in the town at that time, he said.
There had been several renovations to the building's interior during the past century, but no structural alterations.
The building has recently been painted inside and its roofing tiles cleaned.
A book outlining the history of the church was launched at the celebrations.
It was written by Dunedin priest Kevin Morton, who is believed to be the only priest in the diocese to have been baptised at the church.
"All my family were from here and many still live here, so I have very strong links with the area," Fr Morton said.
The book took him abut two years to complete.
"It started off being a book about the building but ended up a history of the parish from its very beginnings."
