Substitute Erik Lamela broke down the right-hand side in the 93rd minute and played a low cross into the Brazil international, who impudently flicked the ball into the net.
The win was a just reward for the visitors after they dominated large parts of the game, but Paulinho's strike was harsh on Cardiff goalkeeper David Marshall.
Marshall made superb stops from Roberto Soldado and Christian Eriksen in the first-half, before repeating the trick after the break to deny Paulinho and Soldado again.
Hugo Lloris was rarely tested at the other end as the hosts concentrated on preserving a point, although substitute Peter Odemwingie did come close to a debut goal.
Malky Mackay made two changes to his Cardiff side, with experienced pair Craig Bellamy and Marshall both returning to the starting line-up. Bellamy took the captain’s armband as he replaced Don Cowie, while Marshall came in for Joe Lewis in goal.
There was just the one change for the visitors from their win over Norwich, meanwhile, as Andre Villas-Boas brought in Kyle Naughton for the injured Danny Rose at left-back.
Cardiff started at a ferocious pace and felt their opponents should have been reduced to 10 men in the opening five minutes after goalkeeper Lloris challenged Fraizer Campbell on the edge of the area.
Lloris came sliding out towards the perimeter of his penalty box and cleared the ball with his hand, with the home side insistent the France international had done so outside the area. However, referee Mark Clattenburg waved play on.
When Tottenham did get their attacking game going, they found Marshall in fine form, the 28-year-old making good saves to deny Soldado and Eriksen.
The first came as the former Valencia striker met a low Kyle Walker cross only for the keeper to get down well to deny him, while the second saw Marshall react superbly after Eriksen latched onto the loose ball after another Soldado effort had been blocked.
Marshall maintained his performance in the second half with another wonderful save from Soldado.
The Spain international looked set to break the deadlock after reacting quickest to the loose ball following a Gylfi Sigurdsson strike that crashed onto the crossbar, however Marshall made a superb reaction stop with his legs to continue to frustrate the striker.
Mackay then introduced Odemwingie just after the hour, and the Nigerian nearly capped his debut with a goal.
The 32-year-old’s opportunity arrived three minutes after coming on for Campbell, but he sent his shot just wide of Lloris’ goal after beating Jan Vertonghen.
Aron Gunnarsson had the hosts best chance of the game with 10 minutes to play as Odemwingie pulled a perfect ball back from the byline. The midfielder hit his effort first time but he leant back and sent the ball flying over the crossbar.
And Villas-Boas' side finally broke the deadlock in stoppage time as Lamela played a one-two with Soldado before finding the midfielder, who got in front of his marker to finish smartly from close range.
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