The 32-year-old tore the anterior cruciate ligament in his right knee during a 3-0 La Liga victory over Celta Vigo last week.
Barca have now confirmed the Spain international has gone under the knife in Augsburg.
Valdes, who has previously stated his desire to leave Barcelona when his contract expires at the end of the season, is not expected to return until the end of October, so his illustrious career with the Spanish champions appears to be over and he will also miss the FIFA World Cup in Brazil.
A statement on the Catalan club's official website said: "The Barca keeper has been operated on by doctors Ulrich Boenisch and Ricard Pruna in Augsburg (Germany) for the anterior cruciate ligament tear he suffered last week.
"The knee's internal cartilage has been sewn up and the operation was concluded successfully. Valdes will be out of action for approximately seven months."
Barca have been strongly linked with a move for German goalkeeper Marc-Andre ter Stegen, whose departure from Borussia Monchengladbach has already been confirmed, ahead of next season, but club president Josep Maria Bartomeu has opened the door for Valdes to stay at the club following his injury.
Valdes, part of Barca's first-team squad since 2002, has been strongly linked with a move to wealthy Ligue 1 club Monaco, yet it remains to be seen if the French outfit firm up their reported interest while he is sidelined.
