The Basal Stem Rot (BSR) disease brought by the Ganoderma Boninense pathogen is regarded as a huge killer for oil palm producers’ countries, particularly Malaysia and Indonesia oil palm plantations. Thus, this research tends to analyze BSR disease infection with plant physiology reaction through water use efficiency (WUE) in oil palm to provide a comprehensive understanding since none of the previous studies analyzed this aspect. The objective of this research is to assess WUE performance in BSR disease severity for mature oil palm tree levels through fronds 17 (March and July). Based on general findings, the BSR severity had varying degrees of impact on the WUE parameter especially when compared between the healthy categories (T0) and infected (T1, T2, T3) individuals. Secondly, identify the most significant variables that affect WUE performance in oil palm BSR disease severity. The outcome shows that from both data, photosynthetic rate (P r), transpiration rate (T r), intercellular CO 2 concentration (Ci), and temperature leaf (TempL) variables contribute significantly to the WUE value. Finally, the analysis focused on correlation variables employed with the BSR disease severity. The outcome demonstrates that, except for Chlorophyll Content (F), there is a substantial correlation (0.5 and -0.5) to all variables analyzed.