Pistorius wiped his eyes as Judge Thokozile Masipa handed down the prison sentence for culpable homicide.
Masipa - only the second black woman to rise to South Africa's bench - said the sentence had to be "fair and just to society and to the accused".
There was no immediate reaction from members of the athlete's family, or from relatives of Steenkamp, a 29-year-old law graduate and model.
"Justice was served," said Dup De Bruyn, the lawyer for the Steenkamp family. He told reporters the judge had given "the right sentence".
Pistorius' defence lawyer Barry Roux said he expected the jailed athlete to serve only 10 months of the five-year sentence behind bars, and the remainder under house arrest.
However, South Africa's state prosecuting authority disputed this opinion, saying Pistorius was likely to serve at least a third of his sentence in prison - effectively 20 months.
On a separate firearms charge for which Pistorius was also found guilty, Masipa gave him a three-year suspended sentence.
Steenkamp was killed almost instantly when Pistorius fired four shots through a bathroom door at his luxury Pretoria home on Valentine's Day last year, having mistaken her for an intruder.