India were 350 for five at lunch here on Wednesday after left-arm spinner Paul Harris had Tendulkar caught at slip for 64. Sourav Ganguly was unbeaten on 34.
With the series locked at 1-1 and India seeking to bat South Africa out of the game, Tendulkar started in watchful mode when he resumed on 28 not out.
It took Tendulkar more than an hour to hit his first boundary of the day but in an ominous sign for the South Africans he struck four sweetly-timed fours within 10 deliveries on either side of reaching his second half-century in successive matches.
But then Harris made a ball spin out of the rough outside leg stump and Tendulkar edged it to Jacques Kallis at slip. Tendulkar batted for 187 minutes, faced 130 balls and hit 11 fours.
South Africa, seeking to make good use of the second new ball, were only able to claim one early wicket, when Dale Steyn bowled VVS Laxman for 13 with a fast, straight delivery which uprooted the off stump. The breakthrough came in the eighth over of the morning.
Tendulkar and Ganguly added 68 for the fifth wicket before Tendulkar was dismissed.
Ganguly ducked into a Steyn bouncer before he had scored, requiring treatment on the field, and was dropped on 22 when Shaun Pollock could not hold a diving chance at mid-off, halfway to the boundary, off Harris.
Virender Sehwag came in to bat at number seven and immediately went for his shots, hitting two boundaries off Makhaya Ntini and reaching 12 not out off 13 balls.
He was beaten by a ball from Harris which spun past his bat in the over before lunch.
India 350 for 5 (Wasim Jaffer 116, Dinesh Karthik 63, Sachin Tendulkar 64, Sourav Ganguly 34 n o; Steyn 2 for 58, Harris 2 for 92, Pollock 1 for 91) Vs South Africa