In April 1578, the Swedish Prince Charles, Duke of Södermanland, visited her home town Heidelberg and proposed.

Maria was brought up to be an ardent Lutheran, and her religion and upbringing according to the principles of the Augsburg Confession was one reason why she was chosen by the sternly Protestant Charles.

Her father accepted the marriage proposal on the condition that she be secured the right to practice her faith in Sweden which was then ruled by Charles' brother John III, who was known for his Catholic sympathies.

They left Germany in July, and in September 1579, Maria received the oath of loyalty from the subjects in her dower lands Gripsholm, Tynnelsö and Rävsnäs estates, Strängnäs city with the parishes Åkers, Selebo and Daga as well as Överenhörna and Ytterenhörna.

[2] Maria is said to have influenced the rule of Charles in the Duchy, intervening on behalf of supplicants and to ask him to show mercy.