Land use/cover change has brought major changes on land surface, including urban heat budget, temperature regimes, urban hydrology and others, leading to unsustainable environments. Remote sensing has played an important role in monitoring these changes across the globe, especially where instrumental data is not available for such observations. The study uses Landsat 5 TM remote sensing data (26 October 2010) to monitor spatial patterns of land surface temperature and urban heat island in the city of Mumbai, India. The thermal data was corrected and converted to top of the atmosphere radiance values and further to temperature in degrees Celsius from Kelvin scale using Erdas Imagine 9.2. The study reveals that urban areas have the highest temperature, ranging from 28°C for low built-up density and 34°C for high built-up and high-rise urban areas. Relatively, lower temperature is associated with forests and water bodies. The temperature varies with the vegetation density and depth of water. High vegetation density is related with low temperature (23°C) and low density with high temperature (26°C). Higher temperature (25°C) is recorded for shallow water and lower temperature (21°C) for deep water. The rocky bare surface record temperature, ranges between 26°C and 28°C. The east–west and north–south profile of surface temperature confirm the heat island phenomena in Mumbai. The central and southern parts of the city have the highest temperature (34°C) whereas the city outskirts have lower temperatures (23°C). For megacities to be sustainable, the spatial spread and composition of urban growth needs to be regulated and constantly monitored.