Tourism is one of the main industries in Nepal. Chitwan National Park (CNP) is one of the rich ecological assets and tourist destinations of Nepal. The study showed that the tourism evelopment in CNP has made significant negative social, economic and environmental impacts to local/community people in the park. It was because of lack of strategic planning for sustainable ecotourism development in the park. The lack of community participation in tourism development, deprivation of local/community people from tourism benefits, loss of traditional occupation and employment, loss of traditional norms, values and cultures, duplication of foreign cultures, high production of pollutions, lack of pollution prevention measures, central controlled planning system, etc were the major constraints for sustainable ecotourism development in the park. The study concluds that there was a need of planning for sustainable ecotourism development in the study area, which was to be based on local community development and community people participative tourism development programmes like community development through ecotourism development in CNP.