One of the most important trends in the modern stage of the socio-economic development of the countries of Southeast Asia is the acceleration of the process of urbanization which will determine the future of the region. By 2050, the share of the urban population in the total population of the region is due to increase to 65% compared to 42% at present. The author stresses that the process of urbanization in SEA has a number of distinctive characteristics. Firstly, it should be noted the uneven distribution of the urban population among the countries of the region. Secondly, there is an accelerated growth of medium-sized cities. Thirdly, in the socio-economic and political systems of Southeast Asian countries, large cities and primarily capitals still dominate Being the foundation of economic growth and social progress, urbanization at the same time has many challenges, one of which is the threat of environmental degradation for almost half of the region’s population. With all the diversity of socio-economic development and the political structure of the countries of the region, the environmental situation in their cities, and especially the capitals, is strikingly similar, which indicates the presence of common causes of environmental crisis. The article notes that environmental tension in cities, primarily subjected to problems associated with urbanization, are at the same time a consequence of the national environmental crisis, the cause of which is the realization of a model of extensive economic development, the implementation of which is accompanied by the over-exploitation of natural resources and increased pollution. The deterioration of the environmental situation in cities, which reveals itself in a high level of air and water pollution, restricting public access to drinking water sources and sanitary facilities, increasing the production of solid waste with imperfect disposal technologies, devalues the results of the economic and social progress of Southeast Asian countries. The author discusses in detail the main environmental problems of cities, analyzes the causes of their occurrence and assesses the possibilities for their prevention. The latter involves an integrated approach to overcoming the environmental crisis along with implementing measures at different levels and in different areas. The author comes to the conclusion that despite the fact that in recent years there have been some positive changes in the approach of the authorities to solving the most acute environmental problems, nevertheless, it is doubtful that the environmental situation will noticeably improve in the near future without changing the philosophy of development itself.