The former Liverpool star is now looking forward to remaining with the Camp Nou outfit for "many more years" after inking a new deal
The Argentina international had already reached an agreement over the new deal at the end of July, and he finalised talks by putting pen to paper on Tuesday.
"I am very happy that a club as big as this has offered to extend my contract," Mascherano was quoted as saying on the official Barca website.
"I can feel relaxed that as long as I do things well, I can stay here for many more years. Ending my playing days in a Barcelona shirt now depends on me and how I perform as a footballer."
The versatile midfielder went on to discuss his side's ambitions for the 2012-13 campaign, and he was clearly feeling positive about the Blaugrana's chances under new coach Tito Vilanova.
"We have high hopes. We're working very hard," he continued.
"The leader is now Tito Vilanova and he will try to adapt his footballing tastes to the team, but the important thing is that, in most ways, it will be much the same as ever."
The 28-year-old Mascherano joined Barcelona from Liverpool in the summer of 2010 and has since become an integral part of the Catalans' first team.