The bottom two teams from the previous season, Llanrwst United and Glan Conwy, were relegated to Division 2 for 2017–18.
Division 2 champions, Llandudno Albion and runners-up, Mynydd Llandegai were promoted in their place.
Llandudno Albion were champions in the previous season and were promoted to Division 1 along with runners-up, Mynydd Llandegai.
The bottom two teams from the previous season were Blaenau Ffestiniog Amateur and Llannerch-y-medd.
Gwynedd League champions, Bodedern Athletic, runners-up, Aberffraw and Vale of Clwyd and Conwy Football League Premier Division champions, Llannefydd were promoted to Division 2.