The former Valencia star has agreed to join the German giants ahead of the 2014-15 season, the club have confirmed
The German champions revealed that the left-footed Spain Under-21 international, who can also play on the wing, has penned a five-year contract and will link up with his new team-mates on Thursday.
"Juan Bernat is an extraordinary young player," Bayern sporting director Matthias Sammer told the club's official website.
"We scouted him for a long time. He is fast, a strong tackler and a real threat to the opposition's goal.
"We are sure that he will prove a very good investment in terms of the future of our team."
Bernat, meanwhile, admitted that he cannot wait to make his first appearance for Pep Guardiola's side.
"I am very happy that I will be able to play for this massive club," he enthused. "Bayern are one of the biggest teams in the world.
"I am very excited to play in a team with [Philipp] Lahm, [Manuel] Neuer, [Bastian] Schweinsteiger, [Arjen] Robben and [Franck] Ribery, and to have Guardiola as a coach."
Bernat, who is a product of Valencia's youth academy, will wear the No.18 jersey at Bayern.