Rats have caused severe problems in oil palm production in Malaysia. Rattus species is the majority group of Muridae found in this area, and it is crucial to know about the species distribution in oil palm plantations (OPP) in Peninsular Malaysia. DNA barcoding method using Cytochrome Oxidase I (COI) gene was performed to identify all rat species captured in OPP aside from morphological identification. The data were then used to estimate the species diversity based on palm tree age. A total of 341 rats were captured and identified as Rattus tiomanicus, R. argentiventer, R. rattus diardii, R. exulans and R. tanezumi. Among these species, R. tiomanicus dominated the plantation with the highest diversity index (H’= 1.31), followed by R. argentiventer and R. rattus diardii. Most species of rats were commonly dispersed in the mature oil palm area. The annual precipitation showed a negative correlation (-0.258, p<0.05) with the species abundance, indicating that rats were more abundant during the dry season. In conclusion, the identification of rat species using molecular tools conforms to the morphological identification to determine the rats’ distribution in the OPP. This can be associated with the oil palm age stage and abiotic factors of seasonal change.