Cesar signed a four-year deal that will keep him at Loftus Road until 2016. The transfer is subject to him receiving international clearance and obtaining a visa.
The 32-year-old's recruitment was another coup for the West London club who have brought in nine new faces during the transfer window including former Manchester United midfielder Park Ji-sung.
"It's fantastic that we've been able to attract a keeper of such outstanding ability to the club," QPR manager Mark Hughes told the club's website.
"When the opportunity to sign a player of his quality presents itself, you have to act quickly and we've managed to get the deal done."
Cesar will now compete for a starting position alongside England international Robert Green, who is feeling the heat after conceding five goals in QPR's opening day loss to Swansea.
"It was always my intention to bring two goalkeepers to the club this summer and now we've got fantastic competition in that department," added Hughes.
Cesar has been capped 64 times by Brazil and in seven seasons at Inter, he won five Serie A title's and a Champions League trophy.
"The English Premier League is the best division in the world," Cesar said.
"Everyone wants to play here and I am no different. Now I just want to give my all to the club and show the fans what I am capable of.
"The desire to achieve things at this club is clear for everyone to see and I wanted to be part of that. I have come here to compete for the shirt and give my all."