The 27-year-old joined Saints in 2014 from Dutch side FC Twente and has scored 13 goals in that time
Speaking to the official website, he said: "I am really pleased
I have had two beautiful years here and a great connection with the supporters and everyone in the club - all the players and the staff
"I am really happy that I have signed a new contract
The club showed a lot of effort to keep me.
"There were also other possibilities, but we recognised that the best is that I stay in Southampton
I want to mention they put in a lot of effort for that - and I appreciate that."
Saints' executive director of football Les Reed added: "I am delighted we have strengthened our commitment with Dusan and that he has added his name to the list of players to have signed new long-term contracts in recent months
"Dusan has been an important part of our success in the past two seasons, with his creativity offering the team a valuable dimension.
"However, it is not just his ability that makes him a key part of the squad, but also his commitment, determination and focus.
"I am confident that, under the guidance of Claude Puel, he will continue to flourish and be a central component of the squad not only this season, but in the years to come."
Source : PA