Slope engineering is primarily focused on landslides nowadays due to increasing number of its episodes. Most of the landslides occur on manmade slopes and it is actually the consequence of the uncertainties carried by different contributing factors. This study explores the causes of Highland Towers 1993 landslide based on reliability analysis technique and taking into account the role of human errors in the contribution of landslide. It is an established fact that the probability of failure derived from structural reliability analysis is conditional which does not incorporate human factors. The analysis considered in this study is based on Monte Carlo simulation by using the commercial slope/w software to evaluate the stability of the slope. The reason for selecting this software is that it combines both deterministic and probabilistic modules which provides more reliable results. These investigations are followed by fault tree analysis (FTA) to quantify the human error causes of failure by determining the chances of landslide governing with different events. The results of FTA show that the potential causes of this landslide are inadequate drainage, failure of rubble wall, and rail pile foundation which confirms that human errors have played a significant role in triggering the landslide. Therefore, this study suggests the use of human reliability analysis technique along with structural analysis to address the risks associated with the slopes. © 2017, Springer International Publishing AG Switzerland.