The 39-year-old, who has made more than 600 appearances for the club, has not played since late April when he ruptured the Achilles tendon in his left foot during a defeat by Palermo.
Despite being faced with a lengthy absence from action which may rule him out until late autumn, the Argentinian insisted he had no plans to retire and now the club have rewarded Zanetti with another year at the San Siro.
Zanetti told intermilan.it: "First of all I'd like to thank the club for the faith they've shown in me.
"We spoke at length about my injury and we decided to do another year.
"They've again shown they believe in me and my passion for Inter.
"I hope I can pay back their affection on the pitch.
"I'd like to thank the many fans who have sent their love over the last few weeks, and they've done likewise with the team in the first few days of the season ticket campaign, showing they'll be with us next season.
"I'm doing everything I can to come back fit and healthy, and to be ready for the coach and my team-mates."