The season began on 13 August 2011 and concluded on 8 May 2012 with Holyhead Hotspur as Division 1 champions, Llanfairpwll and Caernarfon Wanderers, who folded at the start of the 2012–13 season,[2] were relegated to Division 2.
In Division 2, Glantraeth were champions with Llanberis as runners-up.
Conwy United were champions in the previous season and were promoted to the Cymru Alliance.
Caernarfon Wanderers were champions in the previous season and were promoted to Division 1 along with runners-up, Bodedern Athletic.
They were replaced by Gwynedd League champions, Glantraeth who were promoted to Division 2.