The defending champions were Rijeka, having won their fourth title the previous year by defeating Dinamo Zagreb in the final.
The following 48 teams qualified for the competition: The draw for the preliminary single-legged round was held on 20 July 2017 in Zagreb.
** Match played on 13 December at Stadion Rujevica in Rijeka due to inadequate pitch condition at ŠRC Zaprešić.
The semi-final was originally scheduled for 28 February 2018 but was later postponed due to unfavourable weather conditions.
The final was played on 23 May 2018 at Stadion HNK Cibalia in Vinkovci.