An understanding of the nexus between water and energy and greenhouse gas (GHG) emissions is essential for sustainable water resources management. While a number of such studies on understanding this nexus have been carried out in the recent past, there have been virtually no studies that have done so for Asian cities. This study aims to plug this gap by analyzing the water–energy–carbon (WEC) nexus for Bangkok, the capital city of Thailand. Using mostly secondary data, and through interactions with concerned stakeholders, the study revealed that more than 335 GWh of energy is used per year for water supply (0.22 kWh of energy to drive 1 m3 of water from source to tap). About 276 million litres of water is consumed for total power production in Thailand; almost 16% of water supplied annually by the Metropolitan Waterworks Authority (MWA). Of this, 0.625 million litres is consumed by electricity, utilised for water supply in Bangkok. In addition 82.2 billion kgCO2-eq is emitted by the power sector annually and energy associated with water emits 187 million kgCO2-eq/year, equal to 0.11 kgCO2-eq of GHG emission from each 1 m3 of water supplied by the MWA. This study provides information on the WEC nexus in cities as evidenced by Bangkok, which can contribute to the formulation of a policy in water and energy sectors to fulfil the objective of reducing GHG emissions.