The fee is undisclosed but as Town chairman David Cardoza explains Cardiff offered a fee that triggered a release clause in Gyepes' contract and now he's heading to Wales.
"Once Cardiff City offered us a figure that triggered the release clause, we were duly bound to allow Gabor to talk to Cardiff and he has now agreed terms."
"We always knew that he wanted to play in the Championship and we wish Gabor every success and thank him for his efforts."
"He has been a quality player for us over the last eight months and we thank him for that. Our attention now turns to adding to our own squad, and work on that is already well underway."
Gyepes goes straight into the Cardiff City squad for Saturday's home game with Norwich City.