In the main competition, the twelve clubs played each other in a
single round-robin stage called the
Taça Guanabara. The last-placed team was relegated to the
2025 Série A2. The top four clubs qualified for the final stage of the Campeonato Carioca, while the next four clubs (5th to 8th places) qualified for the
Taça Rio. In the Taça Rio, the 5th-placed club faced the 8th-placed club, and the 6th-placed faced the 7th-placed. In the final stage of the Campeonato Carioca, the winner of the Taça Guanabara faced the 4th-placed club, while the runner-up faced the 3rd-placed club. In both of these four-team brackets (the Taça Rio and the final stage of the Campeonato Carioca), the semi-finals and finals were played over two legs, without the use of the
away goals rule. In the semi-finals of both the Taça Rio and the final stage, the higher placed teams in the Taça Guanabara table advanced in case of an aggregate tie. In the finals of both brackets, there was no such advantage; in case of an aggregate tie, a
penalty shoot-out would have taken place. The top four teams of the Campeonato Carioca and the winner of the Taça Rio qualified for the
2026 Copa do Brasil. Should these teams also qualify for the 2026 Copa do Brasil via national and international competitions, their Campeonato Carioca berths will be taken by the next-best team. The top two teams of the Campeonato Carioca that were not already playing in the
Campeonato Brasileiro Série A,
Série B or
Série C qualified for the
2026 Série D. ==Taça Guanabara==