The 30-year-old Argentina international, who joined from French side Montpellier in 2014, has gone on to become a key member of the side and has made 88 appearances in all competitions.
During his time at Allianz Park, Sarries have won two Premiership titles, the European Rugby Champions Cup and the Anglo-Welsh Cup and director of rugby Mark McCall is delighted to tie him down.
"Juan has contributed enormously in his four years at the club," he told the club's website.
"He's a great player, a brilliant character and we're delighted to have him and his family stay at Saracens."
Figallo added: "I'm really happy to stay.
"I've played four seasons here and I've really enjoyed myself.
"My family came here as two; I got married just before I came here and now we have two kids and we're living the Sarries life. We really love it."