The culprits targeted the Hopehall Evangelical Church in Greendykes Road in Broxburn, West Lothian, between 11am on Wednesday and 11am on Thursday.
They smashed two windows in toilets at the 100-year-old church to gain entry before ransacking a room and making off with the hallmark silver items.
The cups and plates were given to the church half a century ago by late members, Mr and Mrs Graham, whose names are inscribed on the metal.
Church elder Adrian Lothian, 71, said: "I don't know why people would steal them as they would not be easy to sell on. The worry for us is that they would simply be discarded somewhere.
"They obviously don't have much of a conscience to break into a church and steal these cups and plates, which have real sentimental value. It's sad that we may never see them again."
Contact Broxburn police station on 01506-852121.