Kulasekara missed the five-match one-day series against the Proteas, which the home team won 4-1 on Wednesday, due to a dislocated finger he suffered during the tri-series in West Indies last month.
Batsman Mahela Jayawardene and fast bowler Lasith Malinga, who were both rested for the fifth one-day game, were also recalled but there was no place for left-arm spinner Rangana Herath.
The spin bowling will fall to Ajantha Mendis, Sachitra Senanayake and leg-spinner Jeevan Mendis, who was also recalled to the side after being left out of the one-day series.
Sri Lanka are the current number one ranked Twenty 20 team.
The first Twenty20 match will take place in Colombo on Friday, with the second and third on Sunday and Tuesday in Hambantota.
Sri Lanka Twenty 20 squad: Dinesh Chandimal (captain), Lasith Malinga, Kusal Perera, Tillakaratne Dilshan, Kumar Sangakkara, Mahela Jayawardene, Angelo Mathews, Lahiru Thirimanne, Angelo Perera, Jeevan Mendis, Thisara Perera, Nuwan Kulasekara, Suranga Lakmal, Sachithra Senanayake, Ajantha Mendis.
(Editing by Patrick Johnston)
