Chevanton, whose contract with Italian side Lecce expired in the summer, has been training with Harry Redknapp's Sky Bet Championship leaders and has now agreed a deal to remain at Loftus Road until December 24.
"With the injuries we've had to Bobby (Zamora) and AJ (Andy Johnson), we're really short of options in that department," Redknapp told the club's official website.
"Javier has spent time with us and integrated into the group very well. He arrives with a good pedigree and gives us a much-needed extra option in attack."
Chevanton, a 33-year-old with seven goals in 22 international appearances, said: "I am very happy to be here, working with a good manager like Harry Redknapp, for a team which is currently top of the Championship with huge ambitions to return to the Premier League.
"I am really looking forward to the challenge of playing in England. I have scored goals all around Europe and I am confident I can continue that record with QPR.
"When I was younger, I loved watching English football. The atmosphere here is great and when the chance came to join QPR, it was all I wanted.
"I have a great will-to-win and I can't wait to do my best for the club and fall in love with the fans."
Chevanton began his career in his homeland with Danubio before moving to Europe in 2001 when he joined Lecce, who were then in Serie A.
He moved to French club Monaco three years later and then to Spanish side Sevilla in 2006.
Since leaving Sevilla in 2010, Chevanton has had two further spells with Lecce and spent time playing in Argentina.
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- Harry Redknapp