Provisioning large concentrations of professional soldiers in Britain after the invasion in AD 43 was a major challenge for the Roman imperial administration. In a distant frontier province such as Britannia, it is generally believed that locally produced agricultural resources must have been vital in feeding and maintaining the occupying army, but direct evidence for this is limited. This study explores the potential for strontium isotope analysis (87Sr/86Sr) of faunal dental enamel to provide new insights for the provisioning of animals to the legionary fortress at Caerleon in South East Wales. Results from 37 domestic animals (cattle, caprines and pigs) from the recent excavation of a military store building in Caerleon are presented. Thirteen faunal dentine and modern plant samples were also analysed to characterise baseline signals for the local landscape. These results indicated an unexpectedly wide range of bioavailable 87Sr/86Sr in the local area, meaning identifying allochthonous individuals with confidence is difficult. The faunal dataset is also very wide ranging, but at least seven individuals can be identified as originating from beyond the local region, with some likely being brought from a substantial distance away. It is highly likely, however, that this underestimates the proportion of animals reared outside the fortress’ immediate hinterland and individuals that fall within the diverse local range could also have been from further afield. This has implications for understanding how the Roman legion was sustained, as well as the impact that provisioning the army had on the countryside, particularly around military sites.