Blues boss Steve Bruce has been hoping to land the Northern Ireland international since the start of the month, but injury has held up the move.
Hughes has finally recovered to full fitness and Bruce has signed him on loan until the end of the season.
Bruce will hope that Hughes will help boost his side's promotion push as they make a late run for a place in the play-offs.
Wimbledon have feared losing the former West Ham and Manchester City ace for some time as they try to reduce the wage bill at Selhurst Park and if he impresses at St Andrews he could make the move permanent.
