The draw was held on 5 July 2018 at the Mediapro Auditorium in Barcelona. The 24 teams were drawn into four groups of six, with the restriction that teams from the same country could not be drawn against each other. For this purpose, Adriatic League worked as only one country. For the draw, the teams were seeded into six pots, in accordance with the Club Ranking, based on their performance in European competitions during a three-year period and the lowest possible position that any club from that league can occupy in the draw is calculated by adding the results of the worst performing team from each league.
;Notes The fixtures were decided after the draw, using a computer draw not shown to public, with the following match sequence: Note: Positions for scheduling do not use the seeding pots, e.g., Team 1 is not necessarily the team from Pot 1 in the draw.
There were scheduling restrictions: for example, teams from the same city in general are not scheduled to play at home on the same round.
Regular season
In each group, teams played against each other home-and-away in a round-robin format. The group winners, runners-up, third-placed teams and fourth-placed teams advanced to the Top 16, while the fifth-placed teams and sixth-placed teams were eliminated. The rounds were 2–3 October, 9–10 October, 16–17 October, 23–24 October, 30–31 October, 6–7 November, 13–14 November, 20–21 November, 11–12 December, and 18–19 December 2018.
Group A
Group B
Group C
Group D
Top 16
In each group, teams played against each other home-and-away in a round-robin format. The group winners and runners-up advanced to the Playoffs, while the third-placed teams and fourth-placed teams were eliminated. The rounds were 2–3 January, 8–9 January, 15–16 January, 22–23 January, 29–30 January, and 5–6 February 2019.
Group E
Group F
Group G
Group H
Playoffs
In the playoffs, teams play against each other must win two games to win the series. Thus, if one team wins two games before all three games have been played, the game that remains is omitted. The team that finished in the higher Top 16 place will play the first and the third legs of the series at home. The playoffs involves the eight teams which qualified as winners and runners-up of each of the four groups in the Top 16.
Maurice Ndour
UNICS
Kenny Kadji
Tofaş
Giorgi Shermadini
Unicaja
Raymar Morgan
Limoges CSP
Alba 
Erik Murphy
Sammy Mejía
Mornar Bar
Cedevita
Rytas
Artsiom Parakhouski
Dragan Apić
Dylan Ennis
Sam Van Rossom