The 2018-2019 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. At the end of regular season, the top 6 teams play in the Championship Round, while the bottom 8 teams play in the Relegation Round. In the Championship round, each team plays Home/Away matches against the other 5 teams for 10 more matches (36 total). In the Relegation Round, the 8 teams are split into 2 groups of 4 where they play Home/Away matches against the other 3 teams in their group for 6 more matches (32 total). 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, (5) goal difference, (6) total goals scored, (7) Fairplay ranking, then (8) a draw.

Upon completion of the 2018-2019 BUL1 Championship and Relegation Rounds, the 1st and 2nd place teams in each Relegation Round group play in the UEFA Europa League Playoffs. The winner of this playoff plays 1 match against the 3rd place team from the Championship Round.

At the end of the 2018-2019 BUL1 Relegation Round, the 3rd and 4th place team in each group enter into a Relegation Playoff with the 2nd and 3rd place teams from BUL2. 3 winning teams from the Relegation Playoff are promoted to the 2019-2020 BUL1 and the 3 losing teams will be relegated to BUL2.