The 2026-2027 BUL1 consists of a double round robin format where each BUL1 team plays Home-Away matches with the other 13 BUL1 teams, for a total of 26 regular season matches per team. At the end of regular season, the top 4 teams play in the Championship group, teams placed 5th through 8th place teams play in the UEFA Europa Conference League (UEFAECL) group, and teams placed 9th through 14th place play in the Relegation group. In the Championship and UEFAECL groups, each team plays Home-Away matches against the other 3 teams in their group for 6 more matches (32 matches total per team). In the Relegation group, each teams plays 1 match against the other 5 teams in their group for 5 more matches (31 matches total per team). Table ranking ties are broken by (1) head-to-head points, (2) head-to-head goal difference, (3) head-to-head goals scored, (4) head-to-head away goals scored (if only 2 teams), (5) goal difference, (6) total goals scored, (7) Fair-play ranking, then (8) a drawing.

Upon completion of the 2026-2027 BUL1 Championship and UEFAECL Playoffs rounds, the 3rd place Championship team enters into Home/Away highest aggregate goals wins matches against the 1st place UEFAECL Playoffs team.

At the end of the 2026-2027 BUL1 Relegation Round, the 5th and 6th place teams will be relegated to BUL2, and the 4th place team will enter into a Promotion/Relegation playoff match with the 3rd place BUL2 teams.