Carmarthen Old Bridge was a seven-arched masonry structure, probably dating from the fifteenth century. The bridge had been much repaired and altered during its life and by the early 1930s it had become so badly damaged by floods that a temporary Bailey-type bridge on timber trestles was erected adjacent on the west side in May 1932, at a cost of £3000, while a replacement bridge was considered.

The old bridge would have been dismantled in 1936 as the new bridge was constructed in 1936-7 more or less on the same site; little of the original bridge would be left except perhaps bases of the river piers.