The environmental ramifications of rapid development on the functioning of warm tropical freshwater ecosystems are poorly understood. Here, a multi-proxy palaeolimnological approach is used to examine the nature and degree of anthropogenic environmental change in a tropical lowland reservoir in Singapore. Singapore has undergone a dramatic transformation over the past century, transitioning from a country with a largely agrarian landscape to one that is highly urbanised. Two radiometrically dated sediment cores were retrieved from one of the country’s oldest reservoirs and analysed for spheroidal carbonaceous particles (SCPs), mercury (Hg), atomic carbon (C) and nitrogen (N), stable C and N isotopes (δ13C and δ15N), and diatoms. The sedimentary data show clear evidence of atmospheric pollution and nutrient enrichment as a result of human activities in Singapore and the region. During the early stages of Singapore’s development (1900s–1960s), the reservoir was minimally impacted and characterised by oligotrophic conditions. As the country began to industrialise and urbanise (1970s–1990s), the SCP data indicate increasing contamination by air pollutants derived from domestic sources of fossil fuel combustion, while the diatom, C/N, δ13C, and δ15N data suggest that the reservoir was becoming more productive, possibly from N depositions arising from an increase in electricity generation and a rapid expansion in transport infrastructure in Singapore. As the pace of development in Singapore slowed down (1990s–the present), the sedimentary data collectively indicate increasing depositions of atmospheric pollutants and nutrient enrichment mediated by a warming climate. A substantial component of increased atmospheric pollution is likely to be of distal, and thus transboundary, origin.