Harry Potter's David Bradley will portray original Who lead William Hartnell in the drama, which will tell the story of the BBC sci-fi drama's creation.
The actor William Russell - who played the Doctor's companion Ian Chesterton - will be portrayed in the biopic by Waterloo Road's Jamie Glover, according to Doctor Who News.
Jemma Powell (Alice in Wonderland) has been cast as Jacqueline Hill - the actress who played Ian's fellow TARDIS traveller Barbara Wright - while Claudia Grant will play Carole Ann Ford, who starred as the Doctor's granddaughter Susan until 1964.
Glover, Powell and Grant join Brian Cox - who will play BBC producer Sydney Newman - and Jessica Raine - cast as Doctor Who's first producer Verity Lambert.
Mark Gatiss - who has written An Adventure in Space and Time - recently admitted that he has dreamt of making the biopic for "years".
"It's a real labour of love for me and I'm just really thrilled that everything's come together for the 50th," he said. "It just seems exactly the right time and a wonderful cast, and it's a very lovely story."
> Doctor Who 50th can replace Olympics and Jubilee, says BBC boss
> Doctor Who anniversary will be "absolutely enormous", says BBC exec
Watch a classic clip featuring the original Doctor Who cast below: