The 23-year-old Brazilian midfielder was forced off during Spurs' 0-0 draw with QPR on Saturday. He underwent an operation on his knee earlier this week.
A short statement on the Tottenham website read: "Following consultation with the knee surgeon, the club can report that Sandro is expected to be sidelined for the rest of the season after surgery on his right knee.
"The Brazil international was forced off during Saturday's game against Queens Park Rangers after injuring both his anterior cruciate ligament and lateral meniscus."
Despite losing such an influential player, manager Andre Villas-Boas says he will stick with the midfielders he currently has at the club, with Jake Livermore's
potential loan-move to Rangers now seemingly in jeopardy.
"The only thing we have done at the moment is hold on to our midfielders, the
ones who are here," Villas-Boas said.
"We have put on hold the movement of Jake Livermore's possible loan to another club. It is not out of the question, I think we are still pretty happy with what we have.
"We have to be careful. We still have a couple of weeks before the market closes, so we have to be careful with the decision and it will be something we hold on to and see how we go."
Sandro has played 27 times this season for Spurs, who are currently fourth in the table with 40 points from 22 games, two points behind third-placed Chelsea.
Tottenham v Manchester Utd is live on Sky Sports 1 this Sunday. For more details click here