This article is about the modern B4328 between Whitland and Tavernspite.
For the former B4328 between Haverfordwest and St Davids, see B4328 (Haverfordwest - St Davids)
The B4328 starts at a roundabout on the Whitland bypass and runs south-westerly along the old route of the A40 into the town itself. Here it turns sharp left to run generally southward before crossing (on the level) the West Wales Line from Carmarthen to Swansea by Whitland railway station and then the River Taf.
The route terminates at a junction with the B4314, just over the Carmarthenshire-Pembrokeshire border at Tavernspite: a place where six roads meet.
The B4328 was first classified between Whitland town centre and Tavernspite at some time in the mid 1930s.