Officially, Sweden was slow in committing herself fully to Protestantism. Traditionally, and with some justification, the parliament (Riksdag) of Västerås in 1527 has been seen as the birth of evangelical Sweden. This view is based on parliament's decision that ‘the word of God should be purely preached all over the kingdom’. However, very little changed within the church in the aftermath of Västerås and none of the Catholic bishops was removed from office. It was not until 1544, during the Succession Parliament which met in Västerås, that it was unambiguously decided to promote Protestantism. It was during this meeting that the king and the representatives of the estates promised never to deviate from ‘the teaching which has become accepted’ and to take action against ‘those who argue against such Christian teachings or try to suppress them’. At this occasion the clergy debated the ecclesiastical ceremonies and agreed to remove some ancient rites which made no sense in an evangelical Lutheran church. The adoration of saints was to be stopped, as was the use of holy water and incense; furthermore, requiem masses and a number of Catholic holidays were no longer to be celebrated.

In Sweden the recently established royal house of Vasa proved of tremendous significance for the introduction and development of the Reformation. The church policies initiated by Gustav Vasa came to determine developments in the reigns of his three sons who succeeded him.