The bottom four teams from the previous season, Llanfair United, Mold Alexandra, Conwy Borough and Buckley Town, were all relegated to various third-tier district leagues for 2017–18. Three teams were successful in the 2016–17 Welsh third-tier leagues and were promoted in their place: Llandudno Junction (Welsh Alliance League runners-up, champions Glantraeth declined promotion), Queens Park (Welsh National League champions) and Rhayader Town (Mid Wales Football League champions).
