The experienced American was on the lookout for a new club after he was released by Reading at the end of last season.
The former Fulham keeper had loan spells with Rochdale and Reading before going on to spend the last seven seasons at the Madejski Stadium.
Hahnemann, 37, has signed an initial one-year deal with the Molineux outfit and will battle it out with Wayne Hennessey for the club's number one jersey.
The veteran is Mick McCarthy's second signing of the summer following the capture of Serbian Nenad Milijas, who is awaiting on a work permit before finalising his switch.
Hahnemann believes Wolves are a massive club and he is relishing the challenge of battling with Hennessey and helping the club retain their top-flight status.
"It's an excellent move for me. Wolves are a massive club and it's another chance to play in the Premier League - that's a huge
draw for me," he told the Express and Star.
"I know I have a real fight to be the number one and no promises have been made. I know I have to go in there, have a good pre-season and then see what happens."