The 29-year-old South African learned his fate at a Pretoria court on Wednesday morning following the killing of model and television personality Steenkamp on February 14, 2013.
Pistorius had been convicted of murder by an appeals court last year, having initially been found guilty of manslaughter in September 2014.
Judge Thokozile Masipa, who oversaw the original trial which led to the manslaughter conviction, opted not to impose the maximum sentence.
In addressing Pistorius, the double amputee who competed at the London 2012 Olympics and Paralympics, she said: “Although a custodial sentence is a proper sentence, I am of a view that a long term of imprisonment will not serve justice in this matter.
“The accused has already served a sentence of 12 months’ imprisonment, he is a first offender and, considering the facts of this matter, he is not likely to reoffend.”
Judge Masipa then announced the sentence, which will see Pistorius likely serve three more years in jail.