Bolton boss Sammy Lee said: "I am delighted that we have finalised the deal to bring Christian Wilhelmsson to Bolton.
"We have been working on this deal for some time and our patience has paid off.
"He is a versatile winger and will add a new dimension to our new style of play we are going to implement this season.
"One of his greatest attributes is that he is capable of playing on both the left and right flank with relative ease.
"He likes to attack and will give us the perfect outlet to provide good service to our attackers."