The 28-year-old double amputee sprinter was found guilty last year of culpable homicide -- a charge akin to manslaughter -- and sentenced to five years in prison for shooting model and TV presenter Reeva Steenkamp on Valentine's Day in 2013.
The Paralympian could be released in August for good conduct after 10 months in jail, three months ahead of the appeal, which will seek a murder verdict that carries more time in prison.
State prosecutors were granted permission to appeal against the verdict, arguing that Judge Thokozile Masipa misinterpreted the law when she ruled Pistorius did not intentionally kill Steenkamp when he shot four times through a locked toilet door.
Pistorius's legal team unsuccessfully tried to halt the appeal, saying the conviction was based on facts presented during the trial and therefore could not be challenged.
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The state argued he deliberately killed the 29-year-old law graduate and reality television star after an argument.
Pistorius, the first double-amputee athlete to compete at the Olympic Games in London in 2012, was jailed after a sensational months-long trial that made world headlines.