The Kwa-Zulu Natal-born defender parted ways with Maritzburg United recently after the two parties failed to agree on financial terms.
According to our sources, Mkhize is expected to sign a three-year contract at the Mayfair club.
"The player has agreed personal terms with Pirates and is expected to sign on dotted line anytime soon," the source tells KickOff.com.
The 27-year-old made 12 starts for his club as they narrowly escaped relegation last season to end the campaign in 14th place.
The Buccaneers have already completed the signing of midfielder Donald Mokondolela from Baroka FC.