The 33-year-old recently began training with the Championship outfit following his release from Stamford Bridge in the summer.
Despite receiving offers from Spain, Benayoun has opted to remain in England with QPR, who are currently second in the league table.
"I am delighted everything is done and am very pleased to join QPR," Benayoun told the club's official website. "The manager (Harry Redknapp) was a very big factor for me. He showed me from the beginning that he really wanted me, and he is someone I have always wanted to play for so I am very happy.
"I have played in the Premier League for the last eight years and I enjoy England very much. The Championship is also a great league and I am looking forward to playing in it and helping QPR build on a great start to the season."
Redknapp added: "Yossi is a good footballer, a top-class player. He's got great ability and is someone I have always liked. I actually tried to take him to Tottenham at one time. I think he will be a fantastic addition to the squad."
Benayoun could make his debut against Blackpool this weekend.