Anthropogenic activities, especially due to agricultural practices, tourism, and other land-use forms, have resulted in serious pollution of Bukit Merah reservoir (BMR), the oldest artificial reservoir in Malaysia since the 1980s. This study assessed the past ecological conditions of the reservoir using ²¹⁰Pb, dating techniques, selected metals, and physicochemical analysis of the sediment core to better manage the reservoir. ²¹⁰Pb results indicated 34 years of human impact on the reservoir, with arsenic recording the least concentrations in the 1980s and the highest concentrations in 2016 and 2018. The minimum and maximum concentrations of lead and cadmium were found in 1990 and 2009. Whereas Copper and Zinc, concentrations peaked in 2012. The mean EF values of metals in the sediment core were above 1 (EF>1), indicating anthropogenic sources. The I_geo values of Arsenic and Cadmium ranged from uncontaminated to strongly contaminated, uncontaminated to moderately contaminated for Lead, Zinc, and Copper. Overall, the dated sediment of BMR revealed that human population growth and increasing economic and agricultural activities coupled with poor land-use forms at the catchment area are the main source of pollution to the reservoir. Therefore, regular monitoring and the enforcement of relevant environmental laws are needed to manage the reservoir.