The 29-year-old has signed a three-year contract with the Portuguese club.
“I am very happy,” the Chilean told Sporting.pt. “I know that I am arriving at a huge club.
“The negotiation process was really complicated, but in the end, everything went well. I have to than the President and Sporting Director for their professionalism throughout the process.
“Both sides will be making financial sacrifices, but we were able to reach a deal because I really wanted to play for Sporting,” Valdes added.