Abstract: In this research, a virgin Oil Shale Powder (OSP) and Oil Shale Ash (OSA) were used as an admixture of cement. The main aim of this study is to compare the compressive strength and setting time properties of mortar mix between the Oil Shale Ash ( OSA) and the Virgin Oil Shale Powder (OSP). Results showed that the compressive strength of mortar cubes containing 10, 20 and 30% OSA decreased by 7.9, 15.8 and 31.6% of reference cement mortar cubes, respectively after 7 days and also decreased by 6.7, 11.1 and 24.4% of reference cement mortar cubes, respectively after 28 days curing compared with strength reference cement mortar cubes. While the strength of mortar cubes containing 10-30% OSP decreased by 21.0, 34.2 and 47.4%, respectively after 7 days curing compared to the strength of reference cubes and decreased by 15.6, 28.9 and 37.8% , respectively after 28 days curing. The reason of decreasing the compressive strength of cement mortar with OSA and/or OSP comparing with pure cement mortar is due to the lower content of ferrous component of OSA and/or OSP in their chemical compositions formulation. The greater reduction in compressive strength of cement with version OSP comparing with OSA is due to the existed oil in the voids of OSP. Setting time of cement paste increased by (23-28), (35-38) and (55-60) min when use cement mortar with 10, 20 and 30% OSA and/or OSP comparing with pure cement mortar due to the slow hydration of cement with OSA and/or OSP. The results of the conducted experiment proved the possibility of reuse oil shale ash as replacement in ratios up to 20% without causing significant effects on the studied properties of cement. The presence of shale in mortar enhances the composite material properties. The results showed an improvement when using cement with OSA or OSP in long time curing.