Chiellini, named Juve's new captain following the departure of veteran goalkeeper Gianluigi Buffon, has signed a two-year deal that runs until 2020.
Defensive partner Barzagli, meanwhile, has signed on for another season that will take him past his 38th birthday next May.
The duo have been core members of a Juve team that has dominated in Serie A, winning each of the past seven league titles.
And coach Massimiliano Allegri, who was previously linked with Arsenal but appears set to stay in Turin, will be able to rely on the experienced pair again for the 2018-19 campaign.
Chiellini is Juve's seventh-longest serving player of all time, having racked up 472 appearances since signing from Roma in 2005.
Despite struggling with a muscle injury in the second half of the season, Chiellini featured in 26 Serie A games last term as Allegri's side held off the challenge of Napoli to win the Scudetto.
When Chiellini and Barzagli have been together on the pitch for Juve, they have conceded an average of 0.7 goals per game and won 2.3 points per match.
"Juventus could not be happier to maintain the services of two men, who for so long have embodied the club's Fino Alla Fine [to the bitter end] mindset," a club statement said.
"Here is hoping for further success for both players and the club starting next season."