The commission was appointed by President Jacob Zuma three years ago to investigate alleged corruption in the country’s multi-billion rand arms procurement deal in 1999.
Mbeki’s appearance would complete the first phase of the public hearings, commission spokesman William Baloyi said in a statement.
Former finance minister Trevor Manuel and former defence minister Mosiuoa Lekota are among those who have testified before the commission, chaired by Judge Willie Seriti in Pretoria.
Manuel testified that a mandate by former president Nelson Mandela to his Cabinet to properly equip the defence force resulted in the arms deal.
Mbeki took over the reigns from Mandela in 1999.
He was meant to have testified before the commission weeks ago, but his appearance was postponed due to the death of his mother, Epainette Mbeki, on June 7.
Government acquired, among other hardware, 26 Gripen fighter aircraft and 24 Hawk lead-in fighter trainer aircraft for the air force, and frigates and submarines for the navy through the deal.