QPR said on the club website that the 30-year-old former Liverpool and Sunderland forward had signed a two-and-a-half year deal for an undisclosed sum.
"I rate Djibril very, very highly," said manager Mark Hughes, who has also signed Nigerian left-back Taye Taiwo, England Under-21 defender Nedum Onuoha and Mali midfielder Samba Diakite since taking over this month.
"I've watched him for many years and always been impressed by what he brings to the table. He's a huge threat to opposition's defences. He's got great pace, power and movement and that's something we'll hopefully benefit from."
"He wanted to sign me at Manchester City and now I am finally here with him at QPR," he said.
"He wants to achieve big things here, that was all I needed to hear from him. I have unfinished business here in England."
