The 25-year-old, who has made 17 appearances for the Brazilian national team, has signed a three-year deal at Loftus Road.
Sandro joined Spurs from Internacional in 2010 and went on to make 81 Premier League appearances, though he had recently fallen down the pecking order after a string of injuries.
Etienne Capoue and Nabil Bentaleb started all three of Tottenham's league matches this season, including a 4-0 win over the Hoops, while the arrival of Benjamin Stambouli has blocked his path to the first team even further.
Instead, Sandro will be reunited with Harry Redknapp, who gave him his Spurs debut while at White Hart Lane, and the star becomes QPR's seventh summer signing.
"He brings energy, aggression, power and quality," enthused Redknapp to the club's official website. "They call him the Beast."
"He’s not only a top quality footballer, but a fantastic boy as well. He’ll lead by example for us."
Sandro added: "I like new challenges and this is one I’m really looking forward to. I will give everything on the pitch and fight for every minute. I’m ready and raring to go."