Kane looked to have sealed Spurs’ exit from Group B when he slotted past Antonio Adan from close range at the last minute, but a VAR review controversially ruled the striker offside.
Marcus Edwards – who came through the Spurs youth system before moving to Portugal – had earlier given Sporting a deserved lead which was canceled out by Rodrigo Bentancourt’s header.
Antonio Conte was sacked for his furious reaction to Kane’s disallowed goal and his side will now need a result in Marseille next Wednesday to qualify for the knockout stages.
Paulinho had already given Spurs a warning before Edwards opened the scoring in the 22nd minute, beating Pierre-Emile Heubjerg’s challenge in a slalom drive before firing into the bottom right corner.
Sporting led throughout the first half and were denied a two-goal advantage when Sebastian Coates inexplicably netted from close range.
It took Spurs 52 minutes to put Adan under real pressure as Eric Dier tested the Spaniard with a fine free-kick before sending a blistering header into the roof of the net.
Sporting missed a huge chance to earn the points through Flavio Nazionale and they paid the price for the waste when Bentancourt rose to nod Ivan Perisic home in the corner with Adan in no man’s land.
However, there was more drama when Kane pounced after Emerson Royal’s knockdown, and after a three-minute VAR review ended up scoring the England captain’s winner.