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As a result of climate change, extreme weather events have been becoming more prevalent in recent years. Rainfall has also become unpredictable, resulting in rainfalls that are more intense and frequent. This will lead to a further increase in rainfall-induced slope failures which can cause detrimental consequences to our environment and society. To prevent such consequences, it is essential to study the characteristics and properties of residual soil slope and its factor of safety. Hence, the objective of this project is to investigate the saturated and unsaturated soil properties together with the factor of safety of residual soil slopes from Jurong Formation in Singapore. Laboratory results were incorporated in Geostudio for numerical analysis for comparison with field instrumentation data. The resulting factor of safety values were then compared with those from an existing slope susceptibility map. The measured soil–water characteristic curve (SWCC) from experimental works in laboratory was within the range of SWCC parameters for residual soil from Jurong formation. The results from numerical analyses indicated that the unsaturated soil properties should be incorporated in the determination of factor of safety of slope either using 2D or 3D analyses. The variations of factor of safety under rainfall loading are attributed to the inclusion of unsaturated soil mechanic principles in the analyses.