The victory gave the visitors a 1-0 lead in the three-match series.
Put in to bat by the hosts, at one point South Africa were in a spot of bother at 110/4; but Klaasen and David Miller (75 not out) stitched an important partnership of 139 runs to set India a 250-run target in 40 overs.
“It was not easy at all (when I went in to bat). The ball was moving around, and just when I went in, it was spinning,” said Klaasen during the post-match presentation ceremony after bagging the ‘Player of the Match’ award.
The 31-year-old South African has an impressive record against India, scoring two half-centuries in T20Is and now a half-century in ODIs as well.
“I don’t know why (the good record against India),” said Klaasen.
The next two ODIs of the series will be played in Ranchi and Delhi.