The 25-year-old midfielder is reunited with former Spurs boss Harry Redknapp under a three-year deal, with the transfer reportedly costing QPR in the region of £10 million.
Redknapp said: "Sandro's a proper footballer and a top-class professional – he's an absolutely fantastic signing for us. I couldn't be more pleased.
"He's been a massive target of mine all summer and I honestly didn't think we'd be able to pull it off – it's a real statement from the club, from the owners, to bring in a player of his undoubted ability.
"He brings energy, aggression, power and quality. 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 did not feature for Tottenham in their opening three matches of the new Premier League campaign and he conceded the prospect of linking up with Redknapp once more was a key factor in his moving across London.
He said: "I like new challenges and this is one I'm really looking forward to. Working with Harry again, who I share a great relationship with, is very special to me.
"Football is in my heart and I'm very happy at this moment. I'm very pleased to be here and I'm looking forward to meeting my team-mates.
"I had a good relationship with the fans at Tottenham Hotspur and I will try my hardest to get the QPR fans to like me."
On his Facebook page, Sandro added: "I'd like to thank Tottenham Hotspur for everything they've done for me. Spurs has been my home since I moved to England and I loved every minute of my time there. To the fans; I'll always have a special relationship with you and can't begin to express how much your support has meant to me, particularly in tough times when I was injured."
