The Iberian medieval period is unique in European history due to the wide spread socio-cultural changes that took place after the arrival of Arabs, Berbers, and Islam in 711AD. Recently, isotopic research has been insightful on dietary shifts, status, resource availability, and the impact of environment. However, there is no published isotopic research exploring these factors in southern Iberian populations, and as the history of this area differs to the northern regions, this leaves a significant lacuna in our knowledge. This research fills this gap via isotopic analysis of human (n=66) and faunal (n=13) samples from the 9th to 13th century Écija, a town renown for high temperatures and salinity. Stable carbon (δ13C) and nitrogen (δ 15N) isotopes were assessed from rib collagen, while carbon (δ13C) values were derived from enamel apatite. Human diet is consistent with C3 plant consumption with a very minor contribution of C4 plants, an interesting feature considering the suitability of Écija to C4 cereal production. δ15N values vary among adults, which may suggest variable animal protein consumption or isotopic variation within animal species due to differences in foddering. Consideration of δ13C collagen and apatite values together may indicate sugarcane consumption, while moderate δ 15N values do not suggest a strong aridity or salinity effect. Comparison with other Iberian groups show similarities relating to time and location rather than by religion, although more multi-isotopic studies combined with zooarchaeology and botany may reveal subtle differences unobservable in carbon and nitrogen collagen studies alone.