The present research is a study on the Assilina assemblages which are recorded from the lower part of the Jarum Formation in the Buldaji section, exposed in the Zagros region, southwest Iran. Studies on the systematic analysis and biostratigraphy of these assemblages resulted in diagnosis of three Assilina taxa: A. ex. interc. cuvillieri Schaub, 1981-tenuimarginata Heim, 1908, A. aspera Doncieux, 1948, and A. aff. aspera (Doncieux, 1948), associated with calcareous nannofossil assemblage. Biostratigraphically, we present new data assignable the SBZ13 and NP15/ CNE9-10 zones from the lower part of the Jahrum Formation (Zagros region) pertaining to the central Tethys. This integrated study indicates a precise correlation between Assilina and calcareous nannofossils zonations of the studied interval at a local stratigraphical scale, enabling us to make possible projections for future stratigraphic studies in the vicinity of Tethyan regions.