Once the darling of the Paralympic movement for pushing for greater recognition and acceptance of disabled athletes, Pistorius shot dead Steenkamp, a model and law student, in his bathroom on 14 February - Valentine's Day - in 2013.
The athlete, known as "Blade Runner" for his carbon-fibre prosthetic legs, went from public hero to convicted murderer in a trial that drew worldwide interest.
He was jailed in 2016, initially for a six-year term, but had that sentence increased to 13 years after an appeal by prosecutors who argued it was too lenient.
The Department of Correctional Services said in a statement that Pistorius, aged 36, had not completed the minimum detention period required to be considered for parole.
"Come August 2024, he would have reached the minimum detention period, then the (parole) board will make a decision," prison spokesperson Singabakho Nxumalo told a media briefing.
"He will have to appear again next year. And then we look into the profile and make a decision in terms of his placement. But for now, it was a matter of saying he has not served the minimum detention period."
Steenkamp's family had opposed the bid, their lawyer Tania Koen said.
"I've just received a call from the parole board. It is a huge sense of relief for June," she said, referring to Reeva's mother.
June Steenkamp had earlier said she was feeling nervous as she arrived at Atteridgeville prison near the capital Pretoria for the closed-door hearing.
"While we welcome today's decision, today is not a cause for celebration," Koen said on behalf of Reeva's parents. "We miss Reeva terribly and will do so for the rest of our lives. We believe in justice and hope that it continues to prevail."
Pistorius' lawyer, Julian Knight, earlier said that Pistorius was due to appear before the parole board to answer questions based on Knight's written submission arguing for his client's release.
Knight had said he did not expect a decision on Friday, 31 March. He was not available to comment after Pistorius was denied parole.
The basis for his argument for Pistorius' parole consideration was that "there doesn't seem to be any negative factors precluding his being released on parole because he meets the requirements of the department in terms of their policies and procedures".
Pistorius, who had both legs amputated as a baby, reached the peak of his fame in 2012 when he became the first double amputee to compete against able-bodied athletes at the Olympics, reaching the 400m semi-finals in London.
A gun enthusiast, he told his trial he had believed Steenkamp was an intruder when he shot her several times through the bathroom door with ammunition designed to inflict maximum damage to the human body.
Pistorius shuffled through the Pretoria court without his prosthetics to show how vulnerable he was faced with the threat of an intruder.
The athlete broke down crying as he told the court that he had been trying to protect Steenkamp when he fired the shots. The prosecutor at the time accused him of using emotional breakdowns to avoid questioning.
He met Steenkamp's father Barry last year when participating in a process known as victim-offender dialogue - part of South Africa's restorative justice programme that brings parties affected by a crime together in a bid to achieve closure.
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