Duminy rescues South Africa against Sri Lanka
David Miller chipped in with 25 during a fifth-wicket stand of 56 with Duminy after the Proteas, electing to bat at the Premadasa Stadium, were reduced to 50-4 in the 11th over.
The tourists are looking to make amends in the three-match Twenty20 series after being trounced 1-4 in the preceding one-dayers.
Off-spinner Sachithra Senanayake, who shared the new ball with Lasith Malinga, struck in each of his first three overs to reduce South Africa to 23-3 by the sixth over.
Senanayake claimed both openers, Quinton de Kock and Henry Davids, leg-before, and then bowled South Africa's Twenty20 skipper Faf du Plessis for eight.
Star batsman AB de Villiers looked good while making 15 when he skied Angelo Mathews to the cover region when Kusal Perera rushed in from the deep to take a good catch.
Duminy hit three boundaries and a six before he was dismissed in the penultimate over, caught in the deep off Ajantha Mendis.