Each of the 16 competitors play each other once in the first stage of the competition, for a total of 15 matches between mid-January and early-April.

If teams are still level, a random draw is made to determine the final order in the standings.

The winners of those contests win promotion to the Campeonato Paulista Série A2 and go on to face one another in the finals, which are also played in a two-legged format.

2025 Série A3 There are all the championship editions, officially recognized by Federação Paulista de Futebol.

a São Bento were saved from relegation due to the withdrawal of Novorizontino in the 2nd level.