The striker, whose deal with Italian side Lecce expired in the summer, has been training with Harry Redknapp's Championship leaders.
And with Andy Johnson and Bobby Zamora currently injured, Redknapp has signed Chevanton until Christmas Eve.
"With the injuries we've had to Bobby and AJ, 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."