Manager Mark Hughes had been keen to land the 32-year-old following QPR's shaky start to the new campaign, which saw the team fall to a 5-0 defeat at the hands of Swansea City on the opening day of the season, then draw 1-1 with Norwich in its second game.
Cesar has committed his future to QPR until 2016, and is likely to make his debut for the club against Chelsea after the upcoming international break.
“It’s fantastic that we’ve been able to attract a keeper of such outstanding ability to the club,” the QPR boss told the club's official 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.
“It was always my intention to bring two goalkeepers to the club this summer and now we’ve got fantastic competition in that department."
Cesar insisted the vision presented to him by both Hughes and club owner Tony Fernandes ensured he had no concerns about joining the west London outfit.
“I’m so happy and excited to be here," Cesar said.
“The ambition of this club was presented to me by the chairman and the coach and I couldn’t have been more impressed.
“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.”
He continued: “The English Premier League is the best division in the world.
“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."