London: Upul Tharanga shared a stand of 69 with Dickwella for the opening wicket before South Africa struck back with quick wickets to pick up 96-run win at The Oval on Satruday.
Sri Lanka allowed South Africa to score just 32 runs in first 10 overs, but later allowed them to get off the hook and post a daunting 299.
Similarly, when they batted, they smashed 87 from their first 10 overs, only to let the momentum fizzle out quickly by getting bowled out for 203.
Chasing a challenging 300 to win, Sri Lanka were off to a flying start, courtesy Niroshan Dickwella.
The exciting wicketkeeper-batsman, who shows glimpses of batting almost in the Sanath Jayasuriya mould, went after the South African bowling in pursuit of the big total. He was severe to both Wayne Parnell as well as Kagiso Rabada, hitting them for boundaries all over the park.
Dickwella brought up Sri Lanka’s fifty in style, in just the 7th over, by hitting Rabada for a six over midwicket.
This is when AB de Villiers introduced the experienced Morne Morkel into the attack, and the senior player did not disappoint.
Morkel got Dickwella caught at the third man on the second ball of his spell, ending the high-flying partnership. Dickwella had done his job though, scoring a brisk 41 off 33 balls.
Kusal Mendis came in and hit a couple of fours, but he was sent back early by Chris Morris in his very first over. De Villiers, who did not do much with the bat, took a one-handed stunner at short midwicket to get rid of him.
Earlier, former captain Amla scored his 25th ODI hundred to help South Africa to 299 for six.
Amla hit five fours and two sixes in his 103 off 115 deliveries before being run out. He added 145 runs for the second wicket with Faf du Plessis (75).
JP Duminy provided impetus to the South Africa innings towards the end, smashing 38 off 20 deliveries with five fours and a six.
Nuwan Pradeep was the most successful Sri Lankan bowler, finishing with two for 54.
Sri Lanka had suffered a blow prior to the match when captain Angelo Mathews was ruled out of the game with a calf strain.
They elected to bowl first after winning the toss in overcast condition.
South Africa - 299 for 6 (Amla 103, du Plessis 75, Pradeep 2-54)
Sri Lanka - 203 (Tharanga 57, Tahir 4-27, Morris 2-32)
Result - South Africa won by 96 runs