Pakistan last month sealed their first-ever ODI series win against the Proteas, beating them 2-1 just weeks after a 4-1 drubbing against the same opposition in the UAE.
Skipper Misbah-ul-Haq, whose side lie sixth in the one-day rankings, two places lower than Sri Lanka, hopes they can build on their success against the South Africans, saying his players thrive under pressure.
"We have good confidence before another tough series and we hope to carry the momentum we gained in South Africa," said Misbah.
But Misbah warned his side against complacency.
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"We must not relax," he said. "Complacency comes when you beat a bigger opponent so we must guard against that because Sri Lanka know these conditions well."
Pakistan will be without lanky paceman Mohammad Irfan -- who stands seven feet one inch (2.15 metres) tall -- after the bowler fractured his hip bone during the Twenty20 series against South Africa last month.
"Sri Lankans are fighters. We need to show our skills and be at our best to beat them," said Misbah.