After spending about $2000 to fix 40 smashed windows at the St Patrick's Basilica last month, two more were smashed at the weekend.
On Saturday, vandals allegedly struck two windows on the south side of the building with stones.
The damage was reported to the Oamaru police about 6pm.
St Patrick's Basilica priest Father Wayne Healey said it was "disappointing" to see more damage to the Oamaru stone building.
"It's very expensive to fix," he said.
"It's not just about getting the window fixed, you've got to get the scaffolding in and it's very expensive."
Father Wayne said he suspected the vandals could have been interrupted, and urged the culprit, or anyone who saw anything suspicious on Saturday, to get in touch with the police.
The vandalism at the Basilica came after a number of other incidents of smashed windows in Oamaru in the last two months.
In December, vandals went on a destructive spree, throwing stones through the windows of eight businesses in one night.
Among those targeted were the Star and Garter Restaurant, Placemakers, which had two windows smashed, Whitestone Cheese and the Waitaki Community Mental Health building.
The Friendly Bay playground was also targeted again, as vandals ripped off the spouting and smashed the electrical box of the shelter.
Oamaru police Sergeant Wayne Brew urged anybody who heard of people involved in the vandalism, or heard windows being broken, not to dismiss it.
"Call us at the time it's happening, on 111 if necessary, and we will respond immediately," Mr Brew said.
"If you hear the sound of broken glass, it usually means a window is being damaged or a burglary is happening."
Anyone with information about the incident can contact the Oamaru police on 03 433 1400 or report anonymously to Crimestoppers on 0800 555 111.