The present rubble exterior is an interpretation of its 15th-century appearance, probably by the architect Frank Shayler, who may also have designed the adjacent Glyndŵr Institute.

[1] The Parliament House is in the centre of the town and is set into a continuous row of frontages midway along Heol Maengwyn, opposite the entrance to Plas Machynlleth and to the left of the Owain Glyndwr Institute.

Tree-ring dating from timber in the building shows that it was felled in 1470,[3] which is two generations later than the parliaments, but the origins of this substantial and important house may be considerably older.

One of the most important features of the Parliament House is a mural by Scottish artist Murray McNeel Caird Urquhart (1880–1972), showing scenes from the life of Owain Glyndŵr.

It comprises a series of 4 large panels depicting scenes from his life, in particular the Battle of Hyddgen, fought on the slopes of nearby Pumlumon in June 1401.

The left elevation of the building features a bay front with a broad-bracketed gable, and diamond-leaded glazed windows with mullions and transoms.

There is a pointed arch doorway to the tower, which features a dog-leg staircase and a partially carved stone handrail inside.