Six months prior to filming, Noomi Rapace started training, learning all sorts of different boxing techniques. This wasn't because these skills would be showcased in the films but to make her body more masculine or androgynous in its appearance. (Although Lisbeth Salander is attracted to both men and women, she never appears truly comfortable in her own skin.) Rapace also worked with a dietitian to help make her as skinny as possible. She also had multiple piercings and learned how to ride a motorbike, earning her license just as filming commenced.
Dr. Anders Jonasson was originally named Anders Jakobsson, after a real-life doctor and close friend of Stieg Larsson. The real Jakobsson, however, confronted Larsson's father and brother about having denied Larsson's partner, Eva Gabrielsson, a share of the literary estate. In retaliation, the surviving Larssons changed the character's name.
Released only two months after A Menina que Brincava com Fogo (2009), this holds the record for shortest gap between film sequels.
The original novel also features a fictional appearance by a real person. In this case, former Prime Minister Thorbjörn Fälldin.
Alexandra Pascalidou: the TV reporter appearing briefly covering the court trial is an actual Swedish TV reporter.