Becoming Astrid is a film that follows the life of Astrid Lindgren as she grows up with her family in the countryside near Vimmerby, Sweden. From the age of 16, she is seen attending church, dances, and helping out on the farm with her parents, brother, and two sisters.
After her essay is published in the local newspaper, Astrid is offered an internship with them. She then has an affair with the older, unhappily-married newspaper editor, which results in her becoming pregnant. The editor sends her to Stockholm for secretarial school and she gives birth in Denmark to avoid divorce complications.
Despite the editor's wishes, Astrid decides not to marry him and chooses to keep her child. This decision leads to a falling out with her family, who disagree with her choice to raise her son instead of leaving him with a foster mother.
Astrid continues to work as a secretary in Stockholm, eventually affording her own flat. When her son finally comes to live with her, he is already several years old. In the end, she reconciles with her family and they welcome their grandson home.