Sligo Rovers were champions, winning their first top league title since 1976–77.
There was a mid-season break coinciding with the Republic of Ireland national football team's UEFA Euro 2012 finals campaign.
On 18 June 2012, Monaghan United announced their withdrawal from the league.
Dundalk win 4–2 on aggregate and retained their place in the Premier Division.
Waterford United appealed the result of the playoff, claiming Michael Rafter was ineligible as Dundalk had incorrectly registered him when they signed him earlier that season.