Top 3 teams of each group advance to qualification round II.

These clubs formed four groups of four and had round robin tournaments at four host cities on 18–20 October.

[4] Main article: 2015–16 LEN Champions League preliminary round The regular season was played between 28 October 2015 and 18 May 2016.

If teams are level on record at the end of the preliminary round, tiebreakers are applied in the following order: In each group, teams played against each other home-and-away in a round-robin format.

[5] Hajós Alfréd Nemzeti Sportuszoda, Budapest, Hungary [6] (Olympiacos) Luka Lončar (Jug) (Szolnok)