The 32-year-old moved to the Nou Camp from Liverpool in 2010 and has made 290 appearances in all competitions.
The Argentina international has yet to score a goal but was signed for his defensive qualities, and his ability to break up play and supply his team-mates has been a huge part of the Catalans' success over the past few years.
The former West Ham schemer will see out this season and two more at Barca before making a decision on his future, and he wants to enjoy every minute of the twilight years of his career.
"I never imagined I would spend so long here. I thought I'd be here for a couple of years, because I knew the demands of the club. It's all gone so quick," he said.
"It's been a pleasure to have spent six years with some of the best players in the history of the club.
"I hope the next three years don't go so quick, because they will be my last here - I want to enjoy them as much as possible."