The team competes in Campeonato Paulista Segunda Divisão, the fourth tier of the São Paulo state football league.

On January 14, 1981,[1] the club was founded by Hermínio Ometto, who was the owner of Usina São João (meaning Saint John's Mill).

União São João won the Campeonato Brasileiro Série C, beating Esportivo Passense of Minas Gerais in the final.

[6] The 1993 Campeonato Brasileiro Série A was expanded to 32 clubs, so, União São João was promoted to dispute the competition.

In the competition's final four, União São João finished ahead of América de Natal, Náutico and Londrina.

União São João's home matches are usually played at Estádio Hermínio Ometto, which has a maximum capacity of 21,000 people.