Costa rejoins the club on a season-long loan, without an option or obligation to buy included.
The 30-year-old spent three seasons with Bayern before departing in 2018, making 50 appearances and winning two Bundesliga titles.
Costa was deemed surplus to requirements by Juventus who will now target Fiorentina forward Federico Chiesa.
Speaking to the club’s official website, sporting director Hasan Salihamidžić said: “Douglas will strengthen us on the outer tracks that are important for our game.
Reflecting on his return to the club, Costa stated: “I am very happy to play for FC Bayern again.
“I had a wonderful time in Munich with many successes and I am sure that we will win titles again now.”
Bayern are still hoping to bring in Marseille defender Bouna Sarr on deadline day having earlier completed a move for free agent Eric-Maxim Choupo Moting.
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Actu monde – NG – Bayern Munich confirm Douglas Costa has rejoined the club