Contrary to the previous editions, this tournament had 10 teams, which was the largest number since the 2011 season, and saw the return of the promotion/relegation playoffs.
Each team plays each other three times for a total of 27 matches in the season.
On 22 December 2016, the FAI announced that the league would be restructured into two 10-team divisions from the 2018 season onwards, one of the recommendations made in the 2015 Conroy Report.
[2] Note: Flags indicate national team as has been defined under FIFA eligibility rules.
Finn Harps won 3–0 on aggregate and were promoted to 2019 Premier Division.