Shikhar Dhawan struck a maiden one-day international century to help India beat injury-hit South Africa by 26 runs and leave the Champions Trophy favourites on the back foot after the opening game on Thursday.
India, hurt by spot-fixing allegations in their home Twenty20 tournament, forgot their worries to seize the initiative in Group B after smacking 331 for seven off their 50 overs and watching South Africa fail to get close.
The gamble to open with Colin Ingram backfired when he was caught in the slips for six and despite Ryan McLaren hammering 71 not out, the Proteas were bowled out for 305.
India opener Dhawan, in his sixth ODI, scored 114 off 94 balls as he stylishly dominated the inconsistent South African bowling which was already without stricken paceman Dale Steyn and lost Morne Morkel to a groin strain when bowling mid-over.
"We got off to a really good start," India captain Mahendra Singh Dhoni told the post-match ceremony.
"The boys played with plenty of aggression but at the same time it was controlled."
R Sharma c Peterson b McLaren 65
S Dhawan c sub b Duminy 114
V Kohli c Amla b Tsotsobe 31
D Karthik c De Villiers b McLaren 14
MS Dhoni c Du Plessis b Tsotsobe 27
S Raina c Duminy b McLaren 9
R Jadeja not out 47
R Ashwin run out 10
B Kumar not out 0
Total (for seven wickets, 50 overs) 331
Did not bat: I.Sharma, U.Yadav
Fall of wickets: 1-127 2-210 3-227 4-240 5-260 6-291 7-323
South Africa innings
H Amla c Dhoni b Yadav 22
C Ingram c Raina b Kumar 6
R Peterson run out 68
AB de Villiers c Jadeja b Yadav 70
JP Duminy lbw b Jadeja 14
F du Plessis c Raina b I.Sharma 30
D Miller run out 0
R McLaren not out 71
R Kleinveldt c Dhoni b I.Sharma 4
L Tsotsobe b Jadeja 3
M Morkel b Kumar 8
Total (all out, 50 overs) 305
Fall of wickets: 1-13 2-31 3-155 4-182 5-184 6-188 7-238 8-251 9-257
The ICC's second 50-over tournament, set to be the final Champions Trophy with a world test championship slated for 2017, opened with a video by Britain's Prince Charles - the Prince of Wales - welcoming teams and fans to Cardiff.
Early temperatures were still lower than average for Britain in June but openers Dhawan and Rohit Sharma soon warmed up the Indian-dominated crowd at a less than full Sophia Gardens.
With the South African field up for the first 10-over powerplay, the pair took advantage with a series of graceful shots as the bowlers struggled to extract any real movement.
South Africa captain AB De Villiers said talisman Steyn should be fit for the second game against Pakistan on Monday and on this evidence, his attack desperately need him back, especially if Morkel is a doubt.
India reached 53-0 after 10 overs and never looked back despite Sharma falling for 65 when he was caught by Robin Peterson off the bowling of McLaren, who ended up as the only South African bowler with any credit with three for 70.
Dharwan had a life on 70 when Morkel failed to pick up a hook at deep backward square and the ball sailed over his head for four after another bad ball by the struggling Rory Kleinveldt.
Virat Kohli (31) came and went before Dhawan was finally caught playing a lofted sweep off JP Duminy.
The South African bowlers limited the damage slightly late on, with big-hitting Dhoni out for 27 but India still scored the highest ODI total at the little-used Cardiff ground as Ravindra Jadeja finished on 47 not out.
Peterson shone in South Africa's reply with a confident 68 before he was run out by Jadeja at mid-wicket after a mix-up with De Villiers (70).
They were ahead of the required run rate early on but wickets began to tumble with the captain going shortly after escaping a run out when he top-edged a pull to Jadeja after clever bowling by Umesh Yadav.
David Miller was run out without facing a ball as Faf du Plessis slipped, leaving the Proteas with too much to do and McLaren's late flurry always looked in vain.
"With the bat in our hand we got ourselves in a great position to win the game," De Villiers said. "We just ran out of wickets.
"I thought we adapted really well and fought back. The game was in our hands, we'll take a lot of positives from that."
The relatively short and uncomplicated Champions Trophy, in contrast to the elongated World Cups of late, has two groups of four with the top two from each going to the semi-finals.
The final is at Birmingham's Edgbaston on June 23 with Cardiff and the Oval in London the other host grounds.
Pakistan play West Indies in Group B at the Oval on Friday.