Southwestern Iran occupies a pivotal position in Iranian archaeological research, particularly concerning the proto-urban and early historic eras. Within this context, the Mehran Plain of Ilam Province is distinguished by cultural remains that are contemporaneous with and analogous to Jemdet-Nasr assemblages. Settlement data indicates that during this era, the Mehran Plain was intrinsically linked to, and shaped by, the environmental and cultural trajectories of Mesopotamia. To elucidate the proto-urban period -a phase defined by profound socio-political and economic complexity-and addressing the limited understanding of this epoch in southwestern Iran, fourteen Jemdet-Nasr pottery sherds from Mehran Plain sites were selected for laboratory analysis, having been procured through excavations and systematic surveys. The study aimed to ascertain whether the Jemdet-Nasr ceramics of the Mehran Plain were manufactured locally or were the products of Mesopotamian specialists imported into the region. Archaeological data from Choghā Ahowān and Choghā Boicheg provides robust evidence for indigenous ceramic production within the plain. Petrographic analysis demonstrated the ubiquitous presence of calcite in all samples, manifesting as both micrite and sparite. These findings are corroborated by XRF results; in certain specimens, calcite exhibits thermal alteration with only reaction halos persisting, whereas in others, its preservation implies firing temperatures did not exceed 800°C. Synthesizing geological surveys of the Mehran Plain with laboratory data, it is deduced that the majority of the pottery was fabricated locally. Consequently, while stylistic attributes, forms, and manufacturing techniques display affinities with Mesopotamian counterparts, these similarities are indicative of cultural interaction rather than direct importation, though validating this hypothesis necessitates further inquiry into production facilities and in situ ceramic assemblages.