The newcomers include Daisy Ridley, who has had small parts in Casualty and Mr Selfridge, and John Boyega, who appeared in London-set sci-fi film Attack The Block.
There have been no details about their exact roles but the pair, along with Domhnall Gleeson from the Harry Potter films, are rumoured to be playing a trio of new lead characters including a teenage orphan girl which were announced during last year's open auditions.
Ford, Fisher and Hamill will return as Han Solo, Princess Leia and Luke Skywalker respectively - the roles that made them huge stars when the first film was released in 1977.
Star Wars: Episode VII is due to begin filming at Pinewood Studios, near London, next month and also see the return of Anthony Daniels, Peter Mayhew and Kenny Baker in their roles as C-3P0, Chewbacca and R2-D2.
The cast, which was announced on StarWars.com and pictured in a photograph of the first read-through, also includes veteran actor Max von Sydow and Andy Serkis, who played Gollum in The Lord Of The Rings.
Also appearing are US actors Oscar Isaac and Adam Driver, who previously shared the screen in the Coen Brothers folk music film Inside Llewyn Davis.
Director JJ Abrams said: "We are so excited to finally share the cast of Star Wars: Episode VII.
"It is both thrilling and surreal to watch the beloved original cast and these brilliant new performers come together to bring this world to life, once again.
"We start shooting in a couple of weeks, and everyone is doing their best to make the fans proud."
The new film is set to be released in December 2015.