Goalkeeper and captain Buffon has penned an extension to keep him in Turin until 2017, while centre-back and vice-captain Chiellini is now tied to the club until 2018.
Buffon's decision to extend his deal could see the 36-year-old Italy shot-stopper end his career at Juve, with whom he has won seven Serie A titles since joining from Parma in 2001.
Both Buffon and Chiellini were said to have turned down the chance to leave Juve earlier in the year.
Speaking at a press conference, they expressed a desire to secure further glory with a team that is seeking a fourth straight Italian top-flight crown.
"As both parties wished to continue, it was the natural choice to extend my contract for another two years," Buffon said.
"The fact that it will be my last contract was a factor, but I’m not worried about that: I feel energised.
"I want to continue performing to a high level, so that I can be an asset and a point of reference for the club."
Chiellini echoed Buffon's sentiments and was quick to praise the club for the impact they have had on his career on and off the field.
"I'm excited to be here. It makes me think back to all the people who've helped me grow and become a man in Turin," Chiellini said.
"Behind our historic achievements there is one big family that works every day to help us achieve our objectives.
"We all continue to have big dreams, with hard work and daily sacrifice as our starting point."
The one achievement that is missing from the pair's list of honours is a UEFA Champions League title, something Buffon is still hopeful of securing.
He added: "Winning the Champions League is not just a personal goal - the best thing would be lifting it and celebrating together."
