Walker, 20, moved to White Hart Lane from Sheffield United in the summer. He was a youth trainee at the Blades when Neil Warnock - now R's manager - was in charge a Bramall Lane.
"QPR are a good, ball-playing team so I am pleased to join the club and hopefully I can improve while I am here," he said.
"I didn't really cross paths with Neil Warnock at Sheffield United because I signed scholarship terms when they got promoted and he left the following season. I didn't have much dealings with him but he's a good guy, a funny guy."
Derby County have signed the Finland international Shefki Kuqi on a three-month loan from Swansea City.
"Shefki has been a potent threat against us in the past and now we hope he can do exactly the same in a Derby County shirt," said the Rams manager Nigel Clough.
"He will give us a presence in attack. He is big, strong and has been a goalscorer wherever he has been."
Gary McAllister, the Middlesbrough assistant manager, has been approached to take a role in Gerard Houllier's backroom staff at Aston Villa.