She was heiress presumptive to the Swedish throne from her birth until that of her brother one year later and again from the start of his reign as King of Sweden, in 1697, until her death and the regent of the duchy of Holstein-Gottorp for her minor son from 1702 to 1708.

Her marriage was arranged as a part of the traditional Swedish policy of alliance with Holstein-Gottorp against Denmark; her brother had earlier been expected to marry Frederick's sister, but he refused.

Hedvig Sophia was regarded to have political influence over her brother the monarch: on 1 October 1702, count Magnus Stenbock gave his spouse countess Eva Oxenstierna the task of using her influence in the parliament to contact Hedvig Sophia and ask her to make Charles XII to end the war and ask for peace.

[8] This led to some strain relation with the administration in Holstein-Gottorp, who was considering a different alliance, but she kept in control of the policy and her line was kept until her death without it leading to any open conflict.

[2] That relationship was open public knowledge at court and seems to have been accepted, though much disliked by her grandmother, Hedwig Eleonora of Holstein-Gottorp.

At the Swedish royal court, Hedvig Sophia was described as a beauty with an interest in fashion, and referred to as "The Happy Princess".

[11] Like her sister, she repeatedly asked her brother for permission to visit him on the battle field during the war, which was common for many other women to do, but he refused them every time.

In July 1709, her brother, who recently had become a refugee of his military catastrophe at Poltava and was far away in Bendery (today in Moldavia) finally received the news of Hedvig Sophia's death in Stockholm the previous December.

[2] In 1716, however, she was hastily buried along with her grandmother without him being asked, as they were worried that he would insist on a funeral of a kind which the country could no longer afford.

[2] She is perhaps most well known for the extensive correspondence between her and her brother King Carl XII, who spent much of his life on war campaigns abroad.