Christianity was originally brought to Switzerland by Roman soldiers and is first attested in the 4th century.

It was declared the sole religion of the Roman empire in 381. Small churches were built in fortified towns, and bishoprics were set up in the main administrative centres.

Western Switzerland remained Christian under the Burgundians, but the Alamans were pagans until the beginning of the 7th century. They were converted by St Gallus, who accompanied the Irish monk Columban first to Zurich and then to Lake Constance. While Columban continued to Italy, Gallus remained with a few companions in eastern Switzerland. Monasteries sprang up, which became centres of learning and culture.

Both bishoprics and monasteries held large amounts of land. The monasteries in particular played an important role in clearing and settling the land, bringing more and more areas under cultivation.

The church's role became highly political. As the German kings tried to strengthen their authority against local nobles, they endowed the church with land in order to gain loyal supporters. Many bishops and abbotts had powers over vassals similar to those exercised by secular lords.

Monasteries were built in strategic areas, for example to secure vital roads to the Alpine passes.