India won the first Test in Johannesburg by 123 runs but South Africa hit back with a 174-run win in the second Test in Durban.
South Africa became only the seventh team to win a three-Test series after losing the first match.
First innings lead
India were dismissed for 414 in the first innings before South Africa replied with 373. The visitors were then bowled out for 169 in their second innings.
The home side were racing towards victory when Smith and Pollock put on 56 before heavy rain started to fall 50 minutes after the start of play.
The pair added another 13 runs before Khan dismissed Smith for 55. Smith started the series badly but made 58, 94 and 55 in his last three innings and captained the side positively in the decisive match.
He was fortunate with the first ball he faced Saturday, scoring four runs off an inside edge against Khan but he set the tone for the morning in Khan's next over when he thumped the bowler past extra cover for four and then played a wristy stroke behind square leg for another boundary.
Pollock was promoted to number four after a wicket fell with the last ball on the fourth day. It proved a positive move as he and Smith scored briskly.
Between them the pair neutralised the threat of Indian leg-spinner Anil Kumble, with Pollock in particular using his feet and taking the attack to the bowler.
Kallis and Prince took 125 minutes and 171 balls over their 77-run stand which ended when Kallis top-edged an attempted pull against Khan and the ball looped gently to Dravid at midwicket.
The all-rounder was out for 32.
Prince hit the winning run when he pushed the ball past Sachin Tendulkar, who came on to bowl in place of Kumble towards the end. He finished with 38 not out.