The competition format suffered changes for a third consecutive season to accommodate a reduction in the number of participating teams, particularly from the LigaPro.
If two or more teams are tied on points on completion of the group matches, the following criteria are applied to determine the rankings: In all other rounds, teams tied at the end of regular time contest a penalty shootout to determine the winner.
Thirty-three teams competing in the two professional tiers of Portuguese football for the 2017–18 season are eligible to participate in this competition.
For Primeira Liga teams, the final position in the previous league season determined in which round they enter the competition.
Twenty teams were paired against each other for ten single-legged ties, while Feirense and Leixões were given a bye to the next round.
[4] Real, who had eliminated Belenenses in the previous round, were disqualified after it was determined that they fielded irregularly a punished player during their second-round match.