The aim of this paper is to examine the demographic transition and the emerging window of opportunities and challenges in Bangladesh. The study utilizes time series data from national level population surveys, censuses and the population projections and estimates produced by the United Nations Population Division. The ongoing demographic transition in Bangladesh leads to many changes in the size and age structure of the rapidly growing population of the country, giving rise to economic and social opportunities as well as policy challenges. The window of opportunity that has emerged since the 1990s will not last long and will not be repeated in the near future. It will reach its peak during the 2020s and will remain open until the 2030s. This demographic dividend needs to be managed efficiently in order to be transformed into better and sustainable economic growth. Understanding demographic challenges must therefore be a priority for the Government of Bangladesh, which must formulate policies to harvest the benefits of the demographic opportunities.