The 34 year-old has put pen to paper on a deal until the end of the season following his departure from Fulham.
Boss Harry Redknapp told the club website: "Aaron's a very experienced player and with the injuries we've suffered lately, he's a fantastic addition.
"He's got pace, excellent positional sense and is a good out-and-out defender.
"He's a great professional and he'll be a big asset to us."
Hughes, who has made 17 appearances for the Cottagers this term, added: "I don't see this as a drop down in class, I see it as a fresh, new challenge.
"It's a chance for me to come and get some games and help this club build on what's been a good season so far.
"It's a different challenge but one I'm really looking forward to."
With Danny Simpson out for the foreseeable future with a back injury, Hughes is in line to make his debut against Burnley on Saturday.
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