Germany booked their place in the last four with a 1-0 victory over France on Friday, before Brazil joined them thanks to a 2-1 triumph against Colombia.
Matthaus feels Luiz Felipe Scolari's men are yet to light up the tournament on the pitch, and has backed his countrymen to progress to the final.
"So far, Brazil have stood out only in the first half of the Colombia game," he told Sky Sport. "Otherwise, I have not seen much, except maybe the euphoria here in the country [Brazil].
"I am a patriot, so I believe in a narrow victory for Germany."
The legendary midfielder also believes the absence of Neymar, who sustained a tournament-ending back injury against Colombia, will come as a huge blow to Brazil's chances, adding: "He is one who has stood out."
Matthaus is Germany's record cap-holder, having made 150 international appearances.
‘He instantly popped into our ratings as one of the best U21 midfielders in Europe. The impressive thing is Slot has made him into more of a no.6' Inside Ryan Gravenberch's transformation at Liverpool
‘I don’t think Liverpool would look at Ollie Watkins, a striker isn’t a pressing issue for them – it’s Arsenal who need one’ Former Reds star explains why his old club don’t need an out-and-out forward this summer
