Forerunner of the WTSWW, the former West Wales Naturalists' Trust traces its origin to a meeting held in Haverfordwest in February 1938.

[1] Seventy-eight people were present at that inaugural meeting and on the motion of Mr. Hugh Lloyd-Philipps, of Dale Castle, the Pembrokeshire Bird Protection Society was formed.

[5] Their work includes reviewing planning applications, managing over 80 reserves, and providing advice to a wide variety of groups.

The suite of reserves includes the Melincwrt waterfalls (near Neath), Coed y Bwl (daffodil woods near Cardiff), Teifi Marshes (near Cardigan, including the Welsh Wildlife Centre, which has a cafe and shop, and is on the Cardigan-Cilgerran Offshoot trail of the Pembrokeshire Coast Path), Castle Woods in Llandeilo (with castle), and the islands of Skomer and Skokholm.

In September 2019 arsonists burnt down a Kingfisher Hide at the Welsh Wildlife Centre, damage which came at a cost of £20,000 to the Trust.