The French midfielder has penned a deal which will keep him at St Mary's Stadium until 2017.
"I am a very happy man," Schneiderlin told the club's official website.
"To commit my future to Southampton is a big thing because this club has big ambitions - and I have big ambitions as well.
"I wouldn't have signed this contract if the club didn't have a big project. When I spoke to the chairman and the manager, I knew they wanted to do something very good at this club and I want to be a part of that.
"My main focus now is to do a great job on the pitch so we achieve all of the ambitions that we have."