The £10,000 ($16,000) prize was given for her story Hitting Budapest about hungry children from a shantytown who steal guavas from an upmarket suburb.
She told the BBC: "I try to write stories that don't normally get told."
The chair of judges said the gang of "poor and violated" children were "reminiscent of Clockwork Orange".
"The language of Hitting Budapest crackles," said judge chair Hisham Matar, who announced the winner at a prize-giving ceremony in the UK city of Oxford on Monday evening.
"This is a story with moral power and weight, it has the artistry to refrain from moral commentary. NoViolet Bulawayo is a writer who takes delight in language."
At the beginning of the story, first published in The Boston Review last year, the narrator explains why the children are heading for Budapest: "There are guavas to steal in Budapest, and right now I'd die for guavas, or anything for that matter."
"There they encounter this lady from London who is more interested in taking their picture, which I guess happens when Westerners go to Africa, but she fails to realise that they are hungry," Ms Bulawayo told the BBC's Network Africa.
One of the children is a 10-year-old girl who has seemingly been made pregnant by her grandfather.
"It's very, very wrong but in this environment it's normalised," she says.
Ms Bulawayo says she identifies with the characters - Darling, Bastard, Chipo, Godknows, Stina and Sbho - and in the story she is "marrying the personal with the imaginary".
"Some of these incidents in Hitting Budapest are taken from my own life - the stealing of guavas to begin with, growing up less privileged and having these dreams."
NoViolet Bulawayo was born and raised in Zimbabwe and recently completed a masters degree at Cornell University in the US.
http://www.bbc.co.uk/news/world-africa-14120349?print=true
