Kara and Hannah, who starred in The Inbetweeners and Hollyoaks, will apparently play the daughters of Harry Selfridge - Rosalie and Violette - in the third series of the period drama.
A source told The Sun: "Kara and Hannah are great additions and everyone is delighted they have been cast as Rosalie and Violette."
Kara rose to fame as Dawn Swann in EastEnders, starring in the BBC1 soap from 2005 until 2009. She then went on to win Strictly Come Dancing in 2010.
Hannah, meanwhile, played the part of Warren Fox's sister Katy in Hollyoaks during 2007. She is also known for her character Tara Brown in The Inbetweeners.
This won't be the first time Kara and Hannah have starred together in front of the camera.
In 2006, the girls were cast as concert-goers in the film Just My Luck, which starred Lindsay Lohan and Chris Pine.
Do you think Kara and Hannah will be good in Mr Selfridge? Tell us below, as the best comment from across the website each week wins £50!