The Polish international joined Juve in 2017 from Arsenal as back-up to club legend Gianluigi Buffon.
“This renewal is a demonstration of the club’s trust in me,” Szczesny told Juventus.
“I’m very happy and I’ll try to give my best. I’ll be here for another four years and I want more titles, I want to win everything. Bet Now on NaijaBet
“You have to sweat, run and sacrifice yourself to achieve this goal that is mine but also that of the club.”
Szczesny joined the club following a two-year loan spell at Roma and has played 84 matches, winning two Serie A titles, one Coppa Italia and an Italian Super Cup.
Juve’s reign as eight-time Serie A champions is under threat this season as they sit in second place in Serie A behind leaders Inter Milan on goal difference.
Third-placed Lazio trail the pair by a point.
Juve play AC Milan in the Italian Cup semifinal first leg on Thursday, and are through to the Champions League last 16 where they will play Lyon later this month.