The £2.25m midfielder is looking to re-boot his career after a lean time at WBA. He was only involved in 13 league and cup games last season and has missed out on Albions pre season campaign.
On Tuesday he told the Echo
"I just want to get back playing football again. And while I can help Cardiff City, they can also help me get my career back on track.
"Call it what you like, and yes, perhaps it could be termed a lifeline, but I really fancy this move to Cardiff City. I see it as a new, fresh challenge. To be honest, I'm really looking forward to the season, I can't wait for it to start.
"I know what I have to do and that it will benefit me and Cardiff City."
Koumas completed the move at Ninian Park on Tuesday evening. An official announcement will be made later today.
It's also expected that Phil Mulryne will complete a move to Cardiff City after a successful loan period. The club expect to announce a third signing as well. An un-named wide midfielder is a possible new player and he's said to be an exciting signing.
Darren Purse is still likely to sign for City and that could happen at any time but it's between the player and his agent.