Shikhar Dhawan smashed a career-best 137 to propel India to a comfortable 307 for seven before the bowlers performed brilliantly to bundle out the Proteas for 177 in 40.2 overs in what turned out to be a rather lopsided contest at the packed Melbourne Cricket Ground.
This was India's maiden World Cup win against South Africa after having lost in 1992, 1999 and 2011.
With two wins from as many matches, India now have a very good chance of qualifying for the quarterfinals as group leaders.
It was yet another commendable show by the Indians, who came into the tournament following a string of poor results in the tri-series.
More From This Section
And Dhoni said what was heartening to see for him as the leader was the team executing its plans on the ground.
"The bowlers bowled in good areas, and even (Ravindra) Jadeja bowled very well, not just quick and flat the way he usually bowls."
The Indian skipper also had words of praise for the team's ground fielding against South Africa.
"I am very pleased with the run-outs. We usually see the oppositions taking on our fast bowlers in the deep. Mohit (Sharma) and Umesh (Yadav) are quite fast and have good arms," Dhoni said.