The Scotland U-21 international, 21, made 25 appearances for the Bluebirds while on loan during 2008/09, and played 10 times for Accrington Stanley during a loan spell last term.
The highly-rated shot-stopper has not made a senior appearance for Leeds and will hope to gain some first-team experience in order to challenge Kasper Schmeichel and Shane Higgs for the number one jersey at Elland Road.