This study examines the failure mechanism and landslide fragility of regular and irregular reinforced concrete (RC) buildings under flow-type landslides. Efficient intensity measures to evaluate landslide fragility of regular flat land buildings and irregular buildings, having step-back and split foundation configurations, are proposed. Further, a methodology is proposed to consider the uncertain flow properties in the investigation of failure mechanisms and landslide fragility. Uncertainty in landslide properties is considered based on some database of past landslide events and laboratory experiments conducted on the soil samples collected from four landslide-active sites in the Mandi district in Himachal Pradesh, India. Overturning moment (hv) is found to be the efficient as well as most proficient intensity measure (IM), among several other IMs for landslide fragility assessment of regular and irregular RC buildings. Further, it is concluded that the landslide performance of RC buildings is directly related to the seismic design level of the building. Moreover, the buildings with step-back configuration are found to be more vulnerable than their split foundation counterparts. Furthermore, structural deficiency of the short columns, typically observed in the considered building configurations, under landslide loading is highlighted and design recommendations are presented for improvements.