Lying on the edge of Selwood forest, Warminster spread out around the course of two streams – from one of which, the Were, the town takes its name; these converged near a confluence with the River Wylye. The name is also applied to a royal manor, which in turn passed on the name to the hundred itself. The combination of the presence of a minster church and the formation of a royal estate with a possibly royal residence indicates some importance of Warminster from perhaps the Early Saxon period. A route between Salisbury and Bath passed close to, if not through, the settlement.

There are other indicators of possible urbanization at Warminster during the pre-Conquest period, but they are not conclusive. Archaeologists found, in one of the secondary streets that backed onto a stream, evidence of small-scale industry by the tenth century or earlier. That a mint was based there from around 979 should, strictly speaking, mean that Warminster was a town, but actual practice did not always adhere to the letter of the law; furthermore no moneyer is known to have operated at Warminster from the reign of the Confessor onwards. There is no evidence Warminster was fortified as a burh, but there were three Iron Age hill-forts on the royal estate, one of which (Battlesbury) was used by the Saxons and would have provided a defensible refuge. Domesday records 30 burgesses at Warminster; however, Haslam, although initially accepting this as evidence of borough status, now believes these burgesses were more likely residents of Wilton borough, but belonging to Warminster in terms of customary dues ["A probable late Saxon burh at Ilchester," 2009, p.10; https://jeremyhaslam.files.wordpress.com/2009/12/a-probable-late-saxon-burh-at-ilchester-1.pdf]. It remains conceivable that at least some were traders and artisans servicing the royal manor and minster church, and such a settlement – the meeting-place of a hundred (on nearby Moot Hill) – is likely to have seen some kind of market activity. Yet the Domesday entry for Warminster gives none of the other usual indicators (e.g. third penny) of borough status. It does mention the obligation to host the royal entourage for one night a year at local expense, as at Bedwyn and Tilshead, but this is characteristic of a royal administrative centre rather than a borough.

Saxon Warminster certainly looks proto-urban, but it is harder to say whether it was ever considered a borough. On the whole the evidence for is a little stronger than the arguments against. But, although any market there may have continued operating after the Conquest, the new Norman monarchy – wary of earlier centres of Saxon royal authority – lacked interest in Warminster, which could have stunted or curtailed further urban growth, until a new landlord was prepared to join the wave of speculative investors seeking new revenues by founding market towns. By 1156 the Crown had granted Warminster to its constable of Salisbury Castle for life, and from 1175 to Robert Mauduit, also constable of that castle as well as a royal chamberlain; he had died by 1191, leaving a minor as his heir. The manor remained the principal residence of the Mauduit family, which survived in the male line as manorial lords down to 1364, when by marriage Warminster passed to the Greene family. It was probably the Mauduits who were responsible for rebuilding and re-dedicating the church in the twelfth century. A market at Warminster is referenced at an unknown date during the lordship of Robert's son Thomas Mauduit, who came of age in 1204 and died ca.1244; that no licence grant is extant (reference to a grant of 1204 in the EUS report is a misreading of evidence cited in the VCH) suggests the market was old enough not to need one, and the jurors at the hundredal enquiry of 1275 were ignorant of what right the Mauduits had to their market at Warminster. The deed mentioning the market also refers to a shop and a chapel there. A tolseld is mentioned in the late fourteenth century, though there is no reason to think this was some kind of town hall, as some suggest. In 1253 Thomas' son William Mauduit acquired the grant of an August fair, which survived up to the early twentieth century, while in 1447 Henry Greene added an October fair, which also long survived.

A manorial extent taken for the inquisition post mortem on Warin Mauduit in 1300 estimated the annual value of the market tolls and the fair at 15s.. The extent also itemized all the freeholders and their rents; although surnames point to a vintner (or his widow), miller, tanner, and a smith's widow, there are no clear signs of burgages – the 12d. rent due from John le Boteler for a messuage with curtilage being an isolated case – and there is no real reason to think the town properties were included in the extent. A different source gives 32s for market tolls for just a six-week period in 1322, which may cast doubt on the reliability of valuations for inquisitions post mortem; however, it perhaps reflects increasing business at Warminster's market, for other figures from later in the century suggest growth – in 1379/80 receipts from stallage alone amounted to £4. – levelling out late in the century and into the first half of the fifteenth. A distinction was made between intrinsec and forinsec traders, and charges set accordingly. By Leland's time Warminster had a reputation as a leading market for grain, which may do much to explain the overall growth pattern in toll receipts. Fair tolls were, in the Late Middle Ages, less lucrative than the market tolls, but nonetheless held fairly steady; livestock, particularly sheep, were likely a leading attraction of the fairs. The local cloth-making industry does not appear to have yet taken the prominent role it would in the economy of the post-medieval town, although dyers are evidenced at Warminster in the fourteenth and fifteenth centuries, and a tailor and skinner in 1338; with the vast numbers of sheep in the region, trade in wool must surely have been important component of Warminster's commerce.

The parish church was situated in the north-west corner of Warminster, with the manor-house south-east of it; both were on a slightly raised area of terrain, almost encircled by streams, which made for marshy ground. The road from the church, which may have been part of the route from Bath, headed south to a junction with roads from east and west, at which point there was a large open area, flanked by streets on north and south sides; it was in the southern street – possibly then no more than a back lane – that the Saxon industrial site was found. This junction area could be a candidate for a Saxon marketplace and mint site – the northern, and (judging from archaeological evidence) more important, street being named Silver Street (a name found in a number of medieval towns, particularly in the vicinity of commercial areas, and possibly indicating the presence of minters/money-changers, though in some places the name was more likely of post-medieval origin) – and local tradition long had it as an older centre of the town. From the east end of Silver Street a second, possibly lesser, route headed north to the manor-house enclosure before continuing on to the church. The two north-south routes formed a loop which likely defined the Saxon settlement.

The road east of the postulated marketplace, after crossing the Were by a bridge, reaches a junction with another street from the north, suggestively named Newport Street (now Portway); this name may imply the existence of an old port (market town). At that junction begins the High Street, along the eastern, wider stretch of which the later medieval market was held, presumably transferred from its older location to where the new traders had immediate access; the fairs probably also took place in this new marketplace. The chapel known to have once stood in the marketplace is believed to have been near the point where what may have been the back lane of Newport Street reached the High Street; this might have been the western end of the marketplace. Settlement east of the bridge, around those two streets, seems to represent a new town probably planted by one of the first Mauduit lords; tenements on either side of the High Street have the typical shape of burgage plots. By the fourteenth century the name Newport was in use for this part of Warminster; a manor of that name, again also known as Portway, was occasionally in the hands of junior members of the family, but whether this included the marketplace is unclear. It may be that this area east of the Were, some distance from the parish church, was chosen as the site of the new town because the lower-lying areas west of the Were were more susceptible to flooding.

Warminster's growth in prosperity is reflected in the number of tax-payers in 1377, which would rank it as tenth in the county. Population expansion in the Late Middle Ages appears to have been at the east end of the High Street, to the west of the Saxon marketplace, and at the north end of Newport Street. Despite this growth, the town community made no evident strides in establishing institutions of self-government; the portmoot court of the Late Middle Ages, over which a portreeve is mentioned as presiding in 1248/49 was almost certainly under seigneurial control, though it is not clear whether its earnings were included among the court profits identified in the extent of 1300. By mid-fifteenth century, however, the old "hall of pleas" had been superseded by one that was above shops – this sounds like the kind of market-located structures known from Thaxted and Titchfield and might point to a little more communal independence in an era when the manorial lords were no longer resident.