Abstract: A detailed study on the microfacies analysis and depositionalenvironments of Tertiary sedimentary rocks exposed in Socotra Island wereconducted. The investigation was based on fifty four samples collected fromfive stratigraphic sections and included four formations from base to top areUmm er Radhuma (Paleocene - Eocene), Dammam (Eocene), Aydim (Upper Eocene) andMughsayl (Oligocene- Miocene). These rock units are mainly composed ofcarbonates. The petrographic study of unstained and stained thin sections havebeen carried out to investigate its sediment logy, microfacies associations anddepositional environments. According to Dunham classification of limestone(1962), eight carbonate facies were distinguished. They are Mudstone, Dolomiticmudstone/wackestone, Fossiliferous wackestone, Packstone, Marly limestone,Sandy limestone, Reefal limestone, Brecciated wackestone/packstone and Chalkylimestone. The recognized microfacies associations were correlated with thestandard microfacies associations (SMA) which were supposed by Wilson (1975)and Flügel (1982 and 2005). The detailed microfacies analysis show that thestudied rock units were deposited within the shallow marine environment exceptthe upper parts of Mughsayl Formation, which were deposited in a slightly deepmarine environment.