The famous sprinter was convicted to six years in prison, significantly less than a 15-year prescribed minimum sentence for murder, the court said on Wednesday.
Pistorius was convicted of killing his partner Reeva Steenkamp on Valentine's Day in 2013. He shot her through a bathroom door. The 29-year-old athlete said he mistook his girlfriend for an intruder and did not intend to kill her.
The South African court acknowledged this argument, but said "the fact that the accused thought it was an intruder does not make it less serious."
Among those factors were the fact that Pistorius attempted to save his girlfriends' life after discovering his mistake and his attempt to apologize to the victim's parents.
The court decided to take his remorse into account upon pronouncing the sentence, as well as Pistorius' health troubles.
"The accused's mental condition has deteriorated during the criminal proceedings" said Masipa.
"He is a fallen hero, who has lost his career and has been ruined financially," she added.
According to media reports, Pistorius would need to spend at least three years in jail before being eligible for parole.
Pressure from the public
The trial has been publicized worldwide for involving a famous athlete and a South African model. Both Pistorius' fans and critics have offered their version of events, including an alleged fight between the couple the evening in question and a history of abuse between the two. The court, however, said media attention should play no role in determining the sentence.
"Our court is a court of law, not public opinion," the judge said.
The decision is the second sentencing in the three-year legal affair. The Paralympian was initially convicted of manslaughter in 2014 and sentenced to five years. He served a year in prison before he was allowed to continue his sentence under house arrest in October 2015.
'Blade runner' in prison
The manslaughter verdict was overturned on appeal from the prosecution. The prosecutors claimed that Pistorius shot with an intention to kill, even if he did not know his girlfriend was in the bathroom.
A double-amputee, Pistorius won several gold medals at the Paralympics and also competed at 2012 London Olympics, drawing international attention by running on his carbon-fiber prosthetics.
Pistorius said he will not appeal Wednesday's sentence.