Norstedts said has signed a contract with I Am Zlatan author David Lagercrantz for a new book featuring the journalist Mikael Blomqvist and hacker Lisbeth Salander.
It is scheduled to be published in August 2015.
The head of publishing at Norstedts, Eva Gedin, said the book will be an original work that includes nothing from the fourth book in the series which Larsson began writing but had not finished when he died in 2004.
Larsson's trilogy has been a huge international success, with more than 75 million books sold in 50 countries. The books have been adapted for the big screen, including a 2011 Hollywood version of The Girl With The Dragon Tattoo starring Daniel Craig and Rooney Mara, and directed by David Fincher.