Merthyr Dyfan contains an old parish church, Barry Rugby Club, Bryn Hafren Comprehensive School and the Master Mariner Pub and Holm View Leisure Centre, although the last two could be considered to be in northern Gibbonsdown.

Of the Dyfan who presumably inspired the name, nothing seems to be known, although the Iolo Manuscripts collected by Edward Williams have led to his popular conflation with the St Deruvian who was added to the King Lucius legends in the 12th century.

[6] Baring-Gould notes Deruvian's "whole history, from beginning to end, is a pure fabrication, and the church of Merthyr Dyfan has been made to serve as a peg to hang it on".

[9] It is now formally dedicated to both Saints Dyfan and Teilo[10] and as recently as 2010 the local parish claimed it to be the oldest Christian site in Wales, citing the legends concerning King Lucius.

Housing development grew up along Merthyr Dyfan hill, north of the original village, in the early 1950s, and the area to the northwest became a council estate, Colcot.