It is imperative that any soil improvement technique can considerably affect the soil media mechanical behavior. However, considering the recent researches, it can be concluded that a combined study on the effect of cement treatment on soil-geotextile interfacial shear strength parameters has almost been neglected. Thus, the main objective of this study is to fill this research gap with the main focus on a selected site in Shiraz city, Iran. In this regard, shear strength parameters of untreated and cement treated soil samples have been acquired by traditional and modified direct shear tests apparatuses. The results indicate that at high cement contents, the soil-geotextile interfacial shear strength increases with an observed behavior similar to over consolidated soils. While up to 1% of cement treatment did not improve the properties, adding 5% and 10% of cement increased both friction angle and cohesion of the soil considerably. Complementary microscopic evaluation of the interface indicated that the interfacial soil-geotextile shear strength is highly dependent upon the soil particles size distribution and specially its fines content. Finally, the numerical modeling of an illustrative reinforced soil structure revealed that knowing the state of stress is a prerequisite to any selection of the soil improvement zone. (C) 2015 Sharif University of Technology. All rights reserved.