The state called for the six-time Paralympic champion to be found guilty of premeditated murder, but Judge Thokozile Masipa believed Pistorius's claims that he mistook his girlfriend Reeva Steenkamp for an intruder when he shot her.
The 27-year-old killed the South African model at his home in Pretoria in the early hours of Valentine's Day last year by firing four gunshots through a toilet door and has been given a five-year jail sentence.
"We were disappointed with the conviction of culpable homicide," said NPA spokesman Nathi Mncube. "We have not made up our minds whether we are going to appeal or not.
"We have 14 days to consider the law and we will [need to] be sure that the facts and law will allow us to appeal."
Pistorius was also given a three-year jail sentence for a firearms offence, which has been suspended for five years.