The water quality in the Terengganu River basin in Malaysia was studied using the Department of Environment-Water Quality Index. Samples were taken at ten locations from July to October 2008. The results showed that human activities are affecting the water quality, with higher pollution levels downstream compared to upstream. Overall, the water quality index ranged from slightly polluted to clean, meeting Malaysia's National Water Quality Standards for most parameters. Continuous monitoring is recommended for better management of the river basin.