The impact of the Degree of Saturation (DOS) on granular Sub Base material was investigated in this study. Seven numbers of CBR (California Bearing Ratio) samples of granular Sub Base material were fabricated at 95% compaction according to Standard Australian, AS 1289.6.1.1. These samples were prepared against the targeted moisture variation between DOS 50% and 70%. In particular, the CBR samples were prepared in the laboratory through proper gradation with optimum moisture content (OMC) and appropriate mechanical compaction. Afterward, the samples were dried back and further soaked to achieve the target DOS. CBR tests were executed to assess the variations in strength and interpret the effect of DOS. The results demonstrated that the bearing capacity of granular Sub Base escalated gradually with the increase of DOS until it reached DOS of 56%, which was corresponding to OMC. Conversely, the bearing capacity declined substantially with the further increment of DOS. The study elaborated that the bearing capacity of Sub Base material can be decreased with the increase of moisture content beyond the OMC level and could also diminish pavement performance, including durability, and lead to moisture-related damage to the flexible pavement.