The twelve winners were decided over one leg, with extra time and penalties if scores were level.
The eight winners were decided over one leg, with extra time and penalties if scores were level.
The four winners were decided over two legs on home and away basis with away goals rule being used.
However, since the cup winners, Olimpija Ljubljana, qualified for the 2018–19 UEFA Champions League as the Slovenian league champions, the spot from the cup was vacated and given to the fourth-placed team in the 2017–18 Slovenian PrvaLiga, Rudar Velenje.
Šoštanj withdrew before the competition began; Triglav Kranj received a bye.