Megacities with populations of more than ten million people in compact urban areas are the most vulnerable environments on Earth. The impacts of climate change on these megacities are multifaceted and severe, especially in developing countries, due to fast growth rate and inefficient adaptation. It is very important therefore to understand the contributions of the growth of megacities to climate change, especially in developing countries. Dhaka, the capital of Bangladesh, is one of the fastest-growing megacities in the world; its population increased from 6.621 million (in 1990) to 16.982 million (in 2014). Today, Dhaka is the 11th largest megacity in the world and is projected to be the 6th largest with an estimated population of 27.374 million by the year 2030. Remote sensing technology has been successfully used for mapping, modeling, and assessing urban growth and associated environmental studies for many years. This research investigates how the intensity of the urban heat island (UHI) effects correlates with continuous decrease in the greenness of the city of Dhaka, as measured from satellite observations. The results of this study indicate that Landsat imagery-derived normalized difference vegetation index (NDVI) can be used to investigate the changes in greenness in the city of Dhaka from 1980 to 2014. The changes in greenness can be correlated with the increase in the intensity of UHI effects in the city of Dhaka as determined using Landsat thermal data from 1989 to 2014.