The United States international believes Fletcher can help Wolves to build on their first season back in the Premier League.
But the 37-year-old is unsure whether Fletcher's arrival will herald another change in tactics by Wolves boss Mick McCarthy.
He switched from a 4-4-2 to a 4-5-1 formation midway through the campaign and it paid handsome dividends with Kevin Doyle operating effectively as the lone striker.
Hahnemann, currently preparing for USA's World Cup clash with England on Saturday, said: "I have seen Steven a few times and there is no doubt that he is a good player.
"He is a dangerous sort of player and I think he will be good for us.
"Our main goal last season was to stay in the Premier League and we achieved that, which was great.
"I think Steven will be good in helping us to build on that.
"There are a few other good guys who have been rumoured to be possible signings for us and we will see who we get."
But in terms of how Wolves may now line-up, Hahnemann admitted: "Who knows how we are going to play?
"We went from 4-4-2 to 4-5-1 which kind of solidified things a bit for us with Kevin up there by himself.
"I don't know if that (Fletcher's signing) is going to change things."
Fletcher, 23, scored 12 goals last season for the Clarets and Wolves confirmed the fee paid equalled the club record for Doyle 12 months ago - believed to be around £6.5million.