The 32-year-old said he would leave the Camp Nou at the end of this season, following 12 years since his first-team debut, in search of a new challenge with a different club.
Valdes was denied the opportunity to say goodbye to supporters on the pitch as he sustained a cruciate knee ligament injury in March that brought a premature end to his season and also scuppered his World Cup hopes with Spain.
In a letter released by the club, Valdes stated his gratitude to the first team trainers starting with Dutch coach Van Gaal "for backing what only he could see in him."
"He (Van Gaal) began building this historic Barca side, which I have been privileged to be part of," Valdes said.
"Thank you Frank Rijkaard, for giving me the confidence necessary, and allowing me to achieve glory, getting my hands on the European Cup in Paris. Wherever you are, I will be indebted to you for the rest of my life Mister."
Valdes also thanked Pep Guardiola, who currently manages Bayern Munich, for guiding and supporting him.
For Tito Vilanova, who passed away last month, he added: "Thank you Tito! Wherever you are, I thank you for having taught us not only the way to keep winning as a team, but also the strength and character needed to face life."
On Monday, Valdes went to the Barcelona training ground to say goodbye to the players, and also thanked his past and present teammates in his message.
"Thanks to all my colleagues with whom I've had the pleasure to work with, that involves wearing the Barca crest on our chests day after day, for making me feel important within the group that we developed over all these years," he said.
"Because it all comes down to this, we are who we are, here and now. Thank you gentlemen!"
Valdes, who also thanked the supporters for keeping him going, will be able to add another trophy to his cabinet if Barcelona win the La Liga title decider against Atletico Madrid at the Nou Camp this weekend.
(Editing by Sudipto Ganguly)
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