The no-nonsense centre-back has been involved in a protracted transfer saga with Pompey and the Students, the former having stalled over financial compensation due to the 12 months remaining on his deal in England.
However, the two clubs appear to have reached an agreement, with Paul Mitchell of Siyavuma Sports, the company that tied up the deal, claiming all paperwork has been filed, and that the 31-year-old is now officially a Clever Boy.
"Yes, Aaron is a Wits player and today he went to training to meet the staff and players," Mitchell is quoted as saying in The New Age.
Mokoena becomes Wits' sixth signing of the off-season, with Mbulelo Mabizela, Tlou Molekwane, Matthew Pattison, Ayo Oluwafemi and Thokozani Mshengu all having signed on over the last few weeks.