In this study, the geochemical analysis of the subgrade at different locations of Ilaro-Papalanto highway was conducted using Atomic Absorption Spectrometry (AAS) and X-Ray Diffractometry (XRD). The predominant oxides present in both soil samples are Silicon Oxide (40% - 45%) and Aluminium Oxide (31% - 34%), and the average silica content of Ilaro and Papalanto are 45.71% and 40.71% respectively, which implies that Ilaro soil sample is more chemically inert and structurally stable than Papalanto soil samples. The average sesquioxide content of Papalanto (36.27%) is higher than that of Ilaro (32.87%), while the silica sesquioxide ratio (SSR) of Papalanto (1.12%) is less than that of Ilaro (1.39%), therefore both soil samples are in advanced stage of weathering but Papalanto soil is more lateritic than Ilaro. Geochemical analysis using XRD indicated the presence of three clay minerals (Kaolinite, Illite and traces of Montmorrrilonite) and one major non-clay mineral, Quartz. The average proportion of Kaolinite in the soil samples are 9% (Ilaro) and 28% (Papalanto), but the average values of Quartz are 62% and 69% for Ilaro and Papalanto, respectively. The higher proportion of sesquioxide and Kaolinite from Papalanto samples is an indication of more failures observed in the region.