Sri Lanka routed South Africa by 128 runs in the fifth and final one-day international in Colombo on Wednesday to wrap up the series 4-1.
The hosts piled up 307/4 after electing to bat and then shot the Proteas out for 179 in 43.5 overs in the day-night game at the Premadasa stadium.
The teams will now play three Twenty20 internationals, with the first match to be held at the same venue on Friday.
Earlier, Tillakaratne Dilshan missed his second successive century by one run as Sri Lanka piled up 307/4.
The aggressive opener, who hit an unbeaten 115 in the fourth game in Pallekele on Sunday, plundered 13 boundaries before he was bowled for 99 by Ryan McLaren in the 39th over.
Lahiru Thirimanne, promoted to number three, scored 68 and Kumar Sangakkara was unbeaten on 75 off 45 balls after Sri Lanka won the toss and chose to bat at the Premadasa stadium.
Sangakkara hit 12 fours, helping the hosts take 52 runs from the final five overs as the South African bowlers wilted in steamy conditions.
Left-handed Thirimanne and Dilshan put on 163 for the second wicket after Kusal Perera was caught behind off Morne Morkel in the fifth over.
Perera was one of the four changes made by the hosts, who have already taken an unassailable 3-1 lead in the series.