County Carlow was divided into three local electoral areas (LEAs) to elect councillors for a five-year term of office on the electoral system of proportional representation by means of the single transferable vote (PR-STV).

At the 2014 Carlow County Council election, there were two LEAs, of 10 and 8 seats.

The terms of reference of the 2018 local electoral area boundary committee required a maximum of seven councillors in each LEA.

Sinn Féin lost two seats, and Cllr John Cassin was re-elected as an Independent.

Labour retained two seats, while Adrienne Wallace, who contested South for Solidarity–People Before Profit in the European Parliament election held on the same day, gained a seat for the party.