The body of the missing 10-year-old was found in the Moretele River in Mamelodi, Pretoria on Sunday, police said.
Katlego Joja from Mamelodi was last seen on May 3 at her home.
Police spokesperson Captain Johannes Maheso said community members spotted the "lifeless body" floating in the river on Sunday.
"We immediately dispatched a team and recovered the body. It has been sent to the government mortuary for an autopsy."
"For now, we are investigating an inquest and that will reveal further information," Maheso said.