The three bells were reported stolen from a house in Wattwil in the canton of St Gallen on Monday.
The large bells were described as being suspended from broad decorated straps and of a type used as musical instruments in traditional festivals.
They had a high collector's value because their rings were specially tuned to harmonize with each other.
The cantonal police said a 29-year-old had returned the bells on Thursday and admitted to breaking into the house and stealing them.
The man said he had acted alone.
Blick reported that it was the second theft of cow bells in two weeks.
At the end of September eight bells of different were stolen from outside a barn in the canton of Solothurn. The replacement value was estimated at 600 to 800 francs a bell.