The first election to the council following the Local Government Act 1972 was held in 1973, initially operating as a shadow authority before coming into its revised powers on 1 April 1974.

The new Rhondda Cynon Taf County Borough Council moved its headquarters to Clydach Vale, using the old building at Pentre as secondary offices for some years before selling it.

the blazon was as follows:[12] Vert a pall wavy argent on a chief indented sable a balance between two acorns leaved and slipped Or, and for a Crest out of a mural crown Sable a demi-dragon gules gorged with a riband pendant therefrom an escutcheon Or charged with three chevrons of the second and supporting a torch erect of the first enflamed proper.

Supporters: On either side a sea-dragon sable the tail proper gorged with a collar checky argent and azure.

The indented edge of the "chief" or upper third of the shield represented the mountainous nature of the valley.

around the dragon's neck hung a shield bearing three chevrons, from the arms of the de Clares, Lords of Glamorgan.