The veteran American stopper moved to Molineux on a free transfer from Reading and is largely expected to provide cover and competition for Wayne Hennessey.
But Hahnemann has revealed to the Express and Star how McCarthy plans to take the top flight by storm next season.
"He has big plans for Wolves and he is confident we can do well next season," said the former Reading keeper, who signed a one-year deal.
"The aim is to try to repeat what we achieved with Reading in our first Premier League season when we finished eighth.
"I've looked at their team and I've been impressed. I also visited their training ground which is unbelievable.
"Wolves are a big club with an amazing set-up and I know I've made the right choice."
McCarthy is looking to add at least another four faces to supplement Nenad Milijas and Hahnemann and his vision is shared by chief executive Jez Moxey.
"I think we've got to try to be as high as possible," said Moxey.
"Psychologically, we're not just talking about finishing fourth bottom but looking to finish as high as possible, and who knows what may happen?
"If you look back to my former club Stoke City, who did so well, I think everybody, including me, thought they would be almost certain to go down.
"But Tony Pulis and Peter Coates and everybody there did a superb job.
"If you can end up mid-table as they did in their first season, that would be remarkable."
Hahnemann said meeting McCarthy convinced him Wolves was the right place to come.
"I was surprised by how quickly Wolves initiated it and got it done.
"I spoke to Mick McCarthy about his plans. We both had questions to ask and it was a great to meet him.
"I had already spoken with Kasey Keller about Mick because they were together at Millwall.
"He said Mick was a great guy and to have that kind of recommendation from a good friend meant a lot.
"People have time for Mick and now I can see why."