Organisers for the fight at Kampala's Nambole Stadium said on Thursday that both boxers had signed contracts and predicted a crowd of 80 000 fans.
Holyfield (47-10 with 2 draws) has not fought since losing a points decision to Nikolai Valuev in a WBA title fight in December 2008.
The 47-year-old American, a former world cruiserweight and heavyweight champion, believes a victory could give him a shot at a more prestigious title.
Botha of South Africa (47-4 with 3 draws) has lost to former world champions Mike Tyson, Lennox Lewis, Wladimir Klitschko and Michael Moorer.