Mhlongo was born in Midway-Chiawelo,Soweto, the seventh of nine children, and raised in Soweto. His father, who died when Mhlongo was a teenager, worked as a post-office sweeper. Mhlongo was sent toLimpopo Province, the province his mother came from, to finish high school. Initially failing his matriculation exam in October 1990, Mhlongo completed his matric at Malenga High School in 1991. He studied African literature and political studies at theUniversity of the Witwatersrand, gaining a BA in 1996. In 1997 he enrolled to study law there, transferring to theUniversity of Cape Townthe following year. In 2000 he discontinued university study to write his first novel,Dog Eat Dog.
He has been called, "one of the most high-spirited and irreverent new voices of South Africa's post-apartheid literary scene".