Lithofacies and petrological studies of sandstones from outcrops at the Kulen area were carried out to understand the diagenetic processes, depositional process, and mineral composition of sandstones. Measurement of stratigraphic section and sandstone samples were conducted at three zones of Kulen area, Phnom Takhok (TK), Peah Ang Chub (PAC), and Phnom Mrech (PM) for this study. The sedimentological study provides the information of large -and small-scale variations in lithofacies, sedimentary structures, and rock textures. Petrography analysis is used to identify the mineral composition, diagenesis alteration, relative porosity, and classify the types of sandstones. The results demonstrated that Kulen area consists of lithofacies, such as cross- bedding and massive bedding sandstones, and black shale. Moreover, the zone presents the sedimentary structures as planar cross- bedding, cross-bedding, parallel lamination, normal and reverse graded -bedding. Furthermore, petrography analysis showed that sandstones of Kulen area are classified into quartz –arenite in PAC zone, sublith arenite in TK zone, and quartz wacke in PM zone with an average relative porosity of ~17% which indication as good reservoir quality. The diagenetic process includes compaction, cementation, replacement, and quartz overgrowth. Therefore, this study provided crucial information for further research on sandstone reservoir characterization, factors controlling its properties, and depositional environment.