Rijeka were the defending champions, who have won their first Croatian league title and ended Dinamo Zagreb's consecutive 11-season reign the previous season.
For the 2017–18 Prva HNL, only seven clubs were issued a top level license: Dinamo Zagreb, Hajduk Split, Inter Zaprešić, Lokomotiva, Osijek, Rijeka and Slaven Belupo.
On 23 May 2017, it was announced that all remaining Prva HNL clubs except RNK Split were granted top level license.
Four teams from Druga HNL acquired the top level license: Gorica, Rudeš, Solin and NK Zagreb.
At the end of the season, ninth placed team Istra 1961 will contest a two-legged relegation play-off tie against Varaždin, runners-up of the 2017–18 Croatian Second Football League.