Holders Chelsea edged past their west London neighbours but were helped by a Lee Camp own goal to seal their place in the FA Cup fourth round.
Pizarro celebrates but it was Camp who helped his effort into the net
The Hoops's goalkeeper was helpless as Claudio Pizarro's low drive hit the post, rebounded off Camp's back and bobbled across the line.
Substitute Patrick Agyemang should have slotted past Hilario after the break as the well-organised visitors improved.
Rangers pressed late on but the below-par Blues dug in to progress.
Rarely do Chelsea host a side richer than themselves but their class prevailed in this battle of the billionaires, despite a spirited performance from the team 35 places below them in the league standings.
This local rivalry that has simmered without engagement for 12 years stirred the Hoops into action early on and they denied their neighbours the time and space to create clear chances.
But the visitors' early zest and work rate soon fizzled out and they fell behind on 28 minutes, albeit through a huge slice of fortune.
Pizarro swivelled on the edge of the box and crashed his low shot off the post, only for Camp to inadvertently knock it back in.
The goal settled the home side who wrestled control of the game in midfield with Steve Sidwell dictating the play.
QPR fans could at least take some consolation from the defeat
Shaun Wright-Phillips went close when he fired over from the edge of the box, while Sidwell went even closer when he struck the post with a low drive from 25 yards that had Camp well beaten.
QPR, with five debutants in their starting line-up, failed to seriously trouble Hilario although Agyemang should have slotted past the keeper from close range. Instead, he scuffed his effort into the keeper's arms.
Akos Buzsaky, a former team-mate of Ricardo Carvalho and Paulo Ferreira from their time at Porto, failed to make any impact and was reduced to speculative long shots.
Didier Drogba, bound for the African Cup of Nations on Sunday, made his return from the knee surgery he underwent in early December. But he, and those behind him, struggled to kill off a dogged QPR.
But despite a valiant effort in the last 15 minutes, the four-time winners held out to progress.
Chelsea: Hilario, Ferreira, Ben-Haim, Alex, Ashley Cole, Wright-Phillips (Joe Cole 79), Obi, Sidwell, Sinclair (Drogba 60), Kalou, Pizarro (Ballack 71).
Subs Not Used: Taylor, Belletti.
Goals: Camp 28 og.
QPR: Camp, Hall, Stewart, Barker, Ainsworth (Agyemang 46), Connolly, Mahon, Rowlands, Ephraim (Balanta 65), Blackstock, Buzsaky (Lee 50).
Subs Not Used: Bolder, Walton.
Ref: Mike Dean (Wirral).
BBC Sport Player Rater man of the match: Chelsea's Michael Ballack 8.53 (on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished.