According to Variety, Basinger signed on to play Elena Lincoln, Christian Grey's (Dornan) business partner and former lover who introduced him to S&M.
Hinted at in Universal's first adaptation of the popular erotic romance novel, Lincoln will attempt to push apart Anastasia Steele (Johnson) and Grey.
Universal pictures will be filming the sequel and the final installment in the series, Fifty Shades Freed back-to-back with new director James Foley. Niall Leonard, who is married to series author E.L. James, is penning the script.
Luke Grimes, Eloise Mumford and Max Martini are also set to return for the sequel.
Fifty Shades of Grey premiered at the Berlin International Film Festival in February 2015 and earned over $570 million at the box office. Fifty Shades Darker is set to hit theaters on Feb. 10, 2017 with Fifty Shades Free arriving on Feb. 9, 2018.