He told the club's official site: "I'm really looking forward to my time at The City Ground. Forest is a club with great history and it's an honour to be here."
Forest beat off competition from a number of Premiership clubs including Newcastle and Everton to secure his services.
Forest paid an undisclosed fee believed to be around £100,000 but he is unlikely to feature against Cardiff with international clearance needed before he can play for The Reds.