Statues, crosses, pews and windows were damaged at Our Lady of the Angels in County Down on Wednesday night.
A car parked nearby which belonged to the priest also had its windscreen smashed.
Detectives say there was no sectarian motive for the attack and are appealing for witnesses.
Supt Simon Walls said: "Any attack on a place of worship must be condemned and we are now investigating to find those responsible.
"If you noticed any activity in this area or have any information which may be connected, please contact police in Kilkeel."