Rashied Staggie, leader of the Hard Livings gang, was shot dead early Friday in a car in front of his house in Salt River, police said.
Staggie's killing followed the shooting and death of another gang member in Cape Town's Mitchells Plain on Thursday.
Police have sent forensic experts to the shooting scenes. The motives behind the two killings remain unknown.
On July 18, the South African National Defence Force began deploying troops in parts of Cape Town to help quell rising gang violence which claims dozens of lives every week.