Nilsson was born in Stockholm and attended and trained at the drama school of the Royal Dramatic Theater there. She appeared in the following Ingmar Bergman films:
Maj-Britt Nilsson died in Cannes, France, aged 82. Her death, which was not widely reported outside Sweden, was confirmed by Jon Asp, executive editor of the online publication Ingmar Bergman Face to Face. No cause was announced.
In 1951 she married Per Gerhard, a theater director, who survives her.