Pistorius was originally sentenced to six years in prison for the 2013 murder of his girlfriend, Reeva Steenkamp.
"The sentence imposed by the … [High Court] with respect to murder is set aside and substituted with the following –- the respondent’s imprisonment for 13 years and five months," Justice Legoabe Willie Seriti said.
He said Pistorius should have been sentenced to 15 years, but the Supreme Court of Appeal took into account the time he had already served, News24 reported.
Pistorius was arrested on Valentine’s Day in 2013 –- the day of the killing.
North Gauteng High Court Judge Thokozile Masipa initially sentenced Pistorius to five years for culpable homicide in 2014, News 24 reported.
Pistorius served only 10 months of the five-year sentence in prison before being released and put under house arrest.
The state appealed the culpable homicide conviction, and it was later replaced with murder by the Supreme Court of Appeal in 2016, and Masipa handed down a six-year jail term, News24 reported.
Previously, the six-time Paralympic gold medallist had made history by becoming the first amputee sprinter to compete at the Olympics, in 2012 in London, running on prosthetic "blades.”
He had his legs amputated below the knee as a baby, the BBC reported.