The Africa Cup of Nations will be contested by 24 teams when the next tournament takes place in 2019, in Cameroon.
The Confederation of African Football's executive committee rubber-stamped the proposal on Thursday at a meeting in the Moroccan capital Rabat.
Africa's flagship sporting event has featured 16 teams since 1996.
A decision on whether the finals will be moved from January and February to June and July is still awaited.
The expansion of the tournament could create problems for Cameroon, which will host the next finals, with the Central African nation's sports minister having to deny reports that preparations were behind schedule this week.
The move follows a two-day symposium organised by Caf president Ahmad to discuss the state of African football.
Further changes are expected but have yet to be announced.
Source: BBC Sport