Fist half strikes by Crewe's Richard Walker and Mark Rivers sent QPR tumbling to their fifth straight defeat.
Defender Walker bundled the ball home seven mintues before the break, and Rivers made it two in first half injury time.
The defeat leaves Rangers in the bottom half of the table for the first time since September.
Crewe made the most of their total of just three shots on target, scoring from two of them.
Walker opened the scoring with a point blank header from a David Vaughan corner. Rangers defender Richard Edghill looked to have hooked the ball clear at the near post, but it was ruled to have crossed the line.
Then Rivers got on to the end of a brilliant Crewe move which went from Steve Foster to Kenny Lunt via Dean Ashton. Lunt was left clear to fire a long cross to Rivers, who slammed the ball into an empty net.
QPR should have been ahead as early as the sixth minute when Crewe keeper Clayton Ince was forced into saves from Marc Bircham and then Leon Best, who latched on to the rebound.
Ince then kept out Lee Cook's 20-yard drive with a spectacular diving save.
Best, on his home debut, and substitute Adam Miller had chances to pull one back for Rangers midway through the second half, but they both shot tamely at Ince.
Crewe were content to defend their lead but were left scrambling when QPR reduced the deficit from the unlikely source of Daniel Shittu, who stormed upfield to power in his second goal of the season.
Martin Rowlands had a chance to grab a point for the home side deep into injury time when they were awarded a free kick - moved 10 yards forward after an infringement .
But winger Rowland blasted straight at the visiting keeper.