In front of watching England boss Roy Hodgson at Loftus Road, Kane continued a stellar breakthrough season and moved his tally for the campaign to 26 goals in all competitions at club level.
Eight of those have now comes in his last five Premier League London derbies, with generous QPR defending lending a hand to Kane's strikes in the 34th and 68th minutes.
Fellow England hopeful Charlie Austin passed up three clear chances for Rangers during the first half of an entertaining encounter.
Ex-Tottenham midfielder Sandro reduced the deficit with 15 minutes to play, but Chris Ramsey's team - who were aggrieved to have a strong penalty appeal turned down in each half - remain three points from safety with 10 games remaining.
Rio Ferdinand and Mauricio Isla returned to the QPR starting XI, while Ben Davies replaced Danny Rose at left-back for Tottenham.
QPR striker Bobby Zamora looped a header against the crossbar inside the first minute as his former club made an initially sluggish start.
But it did not take long for Tottenham to find their rhythm and Rangers goalkeeper Rob Green made a magnificent point-blank save to deny Kane from Kyle Walker's right-wing cross.
Walker was almost culpable for QPR taking a 20th-minute lead when Austin turned his ill-advised backwards header goalwards, but Hugo Lloris responded with a superb reaction stop.
Zamora and Austin combined for Matt Phillips to thump wide from inside the area as QPR grew in confidence as an attacking force.
Austin came closer still in the 29th minute as he touched the ball beyond the Tottenham defence and clattered a left-footed shot against the crossbar.
QPR rued those missed chances as Kane headed in from Andros Townsend's floated free-kick, capitalising on disorganised home defending and Green coming out to leave himself stranded.
Isla had penalty claims rejected when he went down under a challenge from Lloris, who saved once more from Austin in first-half stoppage time after Green kept out Walker's deflected drive.
Tottenham began the second half brightly, with Christian Eriksen curling a strike against the post and Kane blasting the rebound off target.
Townsend passed up a 49th-minute opening when Steven Caulker carelessly gave away possession, while Eriksen failed to pick out Nacer Chadli when Tottenham took QPR apart on the break.
Direct play up towards Zamora continued to prove fruitful for Rangers and the targetman drew a sharp near-post save from Lloris in the 57th minute.
Zamora's strike partner Austin was an unlikely hero at the other end two minutes later when he cleared Eriksen's shot off the line.
Midway through the second half, Tottenham's pressure eventually told as Kane sprung a sorry excuse for a QPR offside trap and coolly rounded Green to slot home.
Sandro drilled home from just inside the box to set up a grandstand finish, during which Austin led furious protests for a penalty when Nabil Bentaleb blocked his close-range shot with an arm.
Referee Craig Pawson was again unmoved, allowing Mauricio Pochettino’s team to make it back-to-back Premier League wins following their League Cup final loss to Chelsea.
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