Juve general manager Giuseppe Marotta revealed on Saturday that the Chile international was set for a switch to Loftus Road.
Neither club have confirmed the deal, but the 26-year-old full-back stated on Twitter on Tuesday that he had finalised his transfer to the London club.
He tweeted: "A new challenge in my career begins.
"I am pleased to be a new QPR player.”
Isla has been with Italian champions Juve for the last two seasons having moved from Serie A rivals Udinese in June 2012.
QPR are also reported to be on the verge of signing Jordon Mutch from Cardiff City as they prepare for their return to the top flight.
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