Despite being highly rated as a youngster the Scotland international leaves the club without having played a first-team game, although he has gained substantial experience during loan spells with Hibs, Darlington, Coventry City and Derby County.
After signing on at Easter Road, he told Hibs’ official website: "I have made no secret of the fact that I love it at Easter Road and Hibernian are a good club with a great squad of young players.
"I've always said that should the opportunity arise to return here I would jump at it - the last time I was here I worked with Bobby Williamson and his coaching staff and now I'm looking forward to doing so again."
Caldwell is the fourth player to leave during the transfer window, following Nikos Dabizas, Carl Cort and Nobby Solano, while Bradley Orr has also joined Burnley on loan.