Four years later Sweden won independence from the Danes under Gustav Eriksson, who was crowned king of Sweden in 1523 as Gustav Vasa. His brother Johannes was named Archbishop of Uppsala and Primate of Sweden by the King. Gustav Vasa sent Olaus to Rome to get confirmation of his brother’s appointment. Over the period of about four years, Gustav changed Sweden’s religion to Lutheranism. During this time and as late as 1534 the king employed the Magnus brothers on various diplomatic missions, particularly with the Netherlands.

They also visited Antwerp, Bremen, Cracow, and Hamburg; Olaus served as secretary to his brother. When King Gustav sent word that Johannes should return to Sweden, the brothers hesitated because of the religious situation, and in 1530 their property was confiscated and their income was cut off. Neither brother ever returned to Sweden again. Apparently they lived on their savings and at times on charity. Johannes continued to write his history of the archbishopric of Uppsala.