Asmari Formation was deposited in the foreland Zagros Basin (southwest Iran). In this research, biostratigraphy related to the Asmari Formation in North of Khorram Abad, Robat Namaki section, is discussed. In the studied stratigraphic section, the Asmari Formation overlies the Shahbazan Formation and underlies Gachsaran Formation and consists of cream to gray medium to thick limestone and marl. A study of 61 samples of the 102 m-thick Asmari Formation led to identification of 4 species and 23 genera of foraminifera. On the basis of the recognized foraminifera, the age of middle part of the Asmari Formation in the studied section is assigned to Early Miocene (Burdigalian) which is comparable to Borelis melocurdica Assemblage Zone. The lower and upper parts of Asmari Formation are characterized without diagnostic microfossils and due to their statigraphical position, assigned to the Aquitanian – Burdigalian, respectively.