Pandy Llywenan was established in 1810 by Sir John Bulkeley as an integrated woollen factory to replace a fulling and dyeing business at Pen Llywenan some 300 metres to the east. It was the first site in Anglesey to bring spinning and weaving into the factory system. The "mill", oriented north-north-east to south-south-west, has two storeys and three bays, and later two-storey and single-storey extensions were added at the north end.. All are built of rubblestone with stone voussoirs over the ground floor opening and timber lintels over first-floor windows, and the pitched roofs are covered with old slates. A wheelpit at the south end contains a small iron overshot wheel with curved sheet-iron buckets, probably a replacement. It was fed from a large pond to the east which was fed from the tailrace of Melin Llywenan (NPRN 96223), and which was already silting up by 1889, the date of the first edition O. S. 25-inch map. A second wheel was added at the north end of the original mill, a site now marked by a passage through the buildings.

In the early twentieth century Pandy Llywenan acquired the corn mill, Melin Llywenan, and extended it to house a self-acting mule; weaving, dyeing and fulling continued at the Pandy. In 1940 both sites were taken over for the making of tweeds, but production ceased in 1955, the last of the Anglesey mills to close.

Information from Cadw Listed Buildings database.
W J Crompton, RCAHMW, 4 December 2014.