Sigrid was born in Svartsjö Castle, Färingsö, to King Eric and Karin Månsdotter before their marriage, but was from the beginning treated as if she was legitimate.

The presence of the children was a way to demonstrate their new status: both of them were officially confirmed as legitimate, and Sigrid and her brother were given all the privileges of a royal princess and prince.

Sigrid was periodically allowed to live outside of the house arrest of her parents, in the care of Herboville and queen dowager Catherine Stenbock.

She was made lady-in-waiting to her cousin Princess Anna of Sweden in 1582, and traveled with her to Poland, where she was present at the coronation of King Sigismund III Vasa in 1587.

It is confirmed that she occasionally had conflicts with Charles IX regarding financial matters, and that the king at such occasions called her a "bastard", but there is nothing to indicate that she was in any way disregarded at court.

Children with Henrik Klasson Tott On 10 September 1609, she married the county chief and royal council judge Nils Nilsson.