Tshabalala crashed home an unstoppable left foot shot high and wide of Mexican goalkeeper Oscar Perez after 55 minutes of a hugely entertaining opening match in Group A on an emotional first day of the first World Cup staged in Africa.
Mexico, who had started brighter, equalised after 79 minutes when Rafael Marquez capitalised on some poor defending and picked his spot to score.
Although South Africa was denied victory, the excitement of the day, against an endless drone of noise from thousands of vuvuzelas, lifted the mood.
But it was a bitter-sweet occasion for millions who woke to the news that Zenani Mandela, the 13-year-old great grand-daughter of former president Nelson Mandela had been killed in a car crash on Friday night.
Mandela, 91, cancelled plans to attend the match which began after opening addresses from FIFA president Sepp Blatter and South Africa president Jacob Zuma who declared the World Cup open.
Mexico took control early on as South Africa made a nervy start with Giovani Dos Santos running the midfield and setting up chances for himself, Guillermo Franco and Carlos Vela as South Africa were forced on the back foot.
Mexico went close to taking the lead after 37 minutes but Vela was ruled narrowly offside after putting the ball in the net and that proved to be the turning point of the game.
South Africa, who had begun to find some rhythym in the later stages of the first half, came out for the second having got over their stage-fright and there were no arguments about them taking the lead with a powerful shot from Tshabalala.
Five minutes later Itumeleng Khune denied Dos Santos with a superb save at the other end before Mexico gained a share of the points with 11 minutes left, although Katlego Mphela almost won the game for South Africa when he hit the post at the end.
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