Reda Khadra’s goal with 12 minutes remaining consigned QPR to defeat against one of their main promotion rivals.
Khadra’s well-struck free-kick from the left caught out keeper David Marshall and ended up in the far corner of the net.
Marshall came on at the interval after Seny Dieng had picked up an injury late in the first half.
Blackburn, who hadn’t scored in their previous five matches, dominated much of the first half and Khadra missed two good chances for them when in on goal, first being denied by Dieng and later dragging a shot well wide.
There was another left-off for Rangers when Bradley Johnson shot tamely at Dieng after Sam Field had lost possession inside his own penalty area.
The visitors did create a couple of decent chances during a lively spell towards the end of the half.
Jeff Hendrick threaded through a clever pass to Albert Adomah, who was denied by keeper Thomas Kaminski, and Ilias Chair shanked wide of the target after being teed up by Chris Willock’s pull-back.
With Charlie Austin unavailable and Lyndon Dykes still out, boss Mark Warburton again deployed Willock up front.
And QPR had to make a change after Dieng was hurt in a collision with Sam Gallagher.
Rangers, now with just one win in six games, rarely threatened an equaliser after going behind.
QPR: Dieng (Marshall 45), Dickie, Dunne, Barbet, Adomah (McCallum 67), Field, Hendrick, Johansen, Odubajo, Chair, Willock (Gray 62).
Subs not used: Amos, Ball, Dozzell, Thomas.