Algeria international Guedioura moves to the Premier League newcomers on a three-year contract for an undisclosed fee, which Press Association Sport believes to be £2.5million.
The 27-year-old joins Ian Holloway's side despite the transfer window closing late on Monday night.
Part of the deal was agreed before the deadline, allowing the club to conclude the transfer on Tuesday.
Guedioura started his career in the French lower leagues before moving to Belgium with Kortrijk and Charleroi, where he was spotted by Wolves.
After a successful loan spell he was brought to Molineux on a permanent deal.
He joined Forest on loan in January 2012, only to become a permanent Reds player later that summer.
Guedioura became a key part of the team, making 35 appearances for the East Midlands club and scoring three goals.
He has been capped 27 times by Algeria, including a substitute's appearance against England in the group stage of the 2010 World Cup in South Africa.