ABSTRACT: The Oligo-Miocene sediments of Central Iran were deposited in part of the Tethyan Seaway connecting the Mediterranean Sea (western Tethys) to the Indian Ocean (eastern Tethys). The Qom Formation sediments were deposited in the northeastern part of the Tethyan Seaway. For analyzing the depositional environments of the Qom Formation in the Tigheh Reza Abad section (type area of the Qom Formation) samples through 967 m thickness were studied which yielded 64 genera and 106 species of benthic and planktic foraminifera, including index species indicative of Aquitanian to Burdigalian age. Five faunal associations (I-V) are recognized on the basis of foraminiferal diversity and abundance. The faunal associations indicate different paleoenvironments along a gradient from inner to outer shelf in the warm, shallow-marine Qom Basin.