The two join a cast that already includes Adam Driver, Oscar Isaac, Andy Serkis, Domhnall Gleeson, Max von Sydow, John Boyega and Daisy Ridley as well as returning stars Harrison Ford, Carrie Fisher, Mark Hamill, Anthony Daniels, Peter Mayhew and Kenny Baker.
"I could not be more excited about Lupita and Gwendoline joining the cast of Episode VII," Lucasfilm president and Episode VII producer Kathleen Kennedy said in a statement on the film's official website.
"It's thrilling to see this extraordinarily talented ensemble taking shape," Kennedy said.
Nyong'o, who won the best supporting actress Oscar for her breakthrough performance in '12 Years a Slave', met with Abrams about a part in the film prior to this year's Oscars.
Christie is best known among her fans as Brienne of Tarth in 'Game of Thrones'. She's also in 'The Hunger Games: Mockingjay - Part 2'.
Being directed by Abrams from a screenplay by Lawrence Kasdan and Abrams, the movie began filming last month in London and Abu Dhabi. It is set to hit theaters on December 18, 2015.
'Episode VII' will be set 30 years after the events in 1983's 'Return of the Jedi'.