Abstarct: Western heights of Shahrood, north of Dehmola village (studied area) is located in the southern part of Eastern Alborz. The purpose of this study was to investigate the deformation pattern of Upper Paleozoic and Mesozoic rock units in the region. For this purpose, outcrops of Jeiroud (Upper Devonian), Shemshak (Lower Triassic-Lower Jurassic), Delichai (Middle Jurassic) and Lar (Upper Jurassic) formations and the boundary between them have been studied. These investigations have confirmed that the dominant structural trend in folding and faulting, follows the structural trend in Eastern Alborz which is northeast-southwest. The boundary between the formations is affected by existence longitudinal faults, for example, F1 and F2 faults can be mentioned which have been given special attention in this study. Both faults with east-west to northeast-southwest trend are part of a fault zone with dominant left-lateral strike slip mechanism such that F1 has provided the placement conditions of Jeiroud Formation with Shemshak Formation and the trace of F2 with the same geometry and mechanism of F1 can be seen on the klippe of Jeiroud Formation on Shemshak. Imposing these faults with left-lateral strike slip mechanism on folded and faulted rock units (affected by old compressive tectonic regime) confirms dominant left-lateral strike slip neotectonic regime in Eastern Alborz. Many signs of this tectonic regime can be seen; for example, we can refer to the Astaneh Quaternary fault with a northeast-southwest trend and left-lateral strike slip mechanism that cut off older folded and faulted rock units.