The 67-year-old has warned his former club against signing the Poland international as they already have enough quality up front
The Bavarians currently have Mario Mandzukic, Mario Gomez and Claudio Pizarro as options up front, and the former Germany coach feels they have no need for another striker.
"Actually, it's not really necessary," the 67-year-old told Sky Germany.
"A big transfer doesn't make any sense to me. When I look at the current squad, I notice that on every position Bayern have two, if not three options.
"Of course I would take Lewandowski. However, assuring him that he's guaranteed to play could be difficult."
Beckenbauer went on to say that Dortmund will push Bayern harder than any other team that they have faced of late in their DFB-Pokal clash on Wednesday.
"I think this will be the biggest challenge in months, with all due respect to Arsenal, of course."
Bayern and Dortmund kick off at 20:30CET on Wednesday.