It lies 9 miles (14 km) west of Brecon on the A40 trunk road to Llandovery, at the point where the Afon Senni flows into the Usk.

One of the factors which influenced the growth of Sennybridge was the establishment of the Neath and Brecon Railway which opened a station in the adjoining village of Defynnog in 1867.

The tramroad, operated by horse-drawn wagons, came down to a loading platform adjacent to the modern A40 road at the west end of the village.

An extensive area of land to the north of Sennybridge is used by the Ministry of Defence for military training purposes.

Sennybridge's primary school, which houses a Welsh Language Unit, utilises the old Secondary Modern buildings in the village.