Filming is set to begin in the UK this month with Jean Marc Vallee directing from a screenplay by Julian Fellowes about the longest serving British Monarch's early years.
Broadbent is currently shooting Indiana Jones 4 and will portray Victoria's uncle King William. Richardson, who will next be seen opposite Vince Vaughn in Fred Claus, will play Victoria's mother the Duchess Of Kent.
Strong, whose credits include Syriana, Sunshine and the upcoming Stardust, has also come aboard in the role of the devious Conroy.
Vallee made his feature film debut with Black List, and went on to win 10 Canadian Genie awards for C.R.A.Z.Y.
The Young Victoria is a GK Films production, and will be produced by King and Scorsese, with Tim Headington and Sarah Ferguson also attached. Denis O'Sullivan will oversee the project for GK Films.