Mbulelo Arthur Nhlauzana (25) pleaded guilty to charges of murder, robbery, and malicious damage to property.
He was arrested in Groutville, on the KwaZulu-Natal north coast, on April 13.
Gasa's body was found floating in the Tugela River four weeks ago. He had sustained multiple wounds. Police found his burnt-out Jaguar near his body.
Residents saw the corpse and called the police, Lieutenant Colonel Vincent Mdunge said.
Eyewitness News named him as Nhlanhla Gasa, an associate to President Jacob Zuma.
Police found his vehicle, a Jaguar, burnt beyond recognition several metres away.
No valuables were taken from the house. A case of murder with aggravating circumstances and malicious damage to property was opened with the Durban North police.
Police said the 63-year-old was attacked at his house and then taken to the river. He is the father of South African television personality Noni Gasa. – Sapa