Ecotourism helps in environmental protection, wildlife conservation, poverty alleviation and socio-economic development. It affects environmental, social and economic components of the community and the whole country. It has different forms which are named according to the preference of the country. Developed as well as developing countries , such as Nepal, are promoting ecotourism for sustainable development of the nation. Different methodologies are applied throughout the world by different researchers for assessing ecotourism. This chapter focuses on review of ecotourism researches throughout the world. It has both positive and negative impacts on environmental, social and economic aspects of the country. Due to the high rate of beneficial impacts, it is helping in the overall development of the community, country and the whole world. There is need of cooperation among different stakeholders, training of ecotourism to tourism entrepreneurs and appropriate management policy for sustainable implementation of ecotourism projects.