This paper focuses on examining environmental implications embedded in recent spatial expansion of the Asian megacities as well as exploring the potentials of planning practices in addressing urban environmental problems. Regardless what underlying forces of recent metropolitan expansion are, nearly all the Asian megacities suffer serious environmental problems as these cities rapidly grow in terms of population and geographical boundaries. Furthermore, the global environmental implication of urban expansion at Asian megacities implies that there must be intense endeavor to develop more innovative policy solution in order to tackle down the worsening urban environmental problems in Asian cities at a metropolitan scale. Given the situation that there has been little attention on environmental consequence of the Asian metropolitan expansion in spatial term, this paper presents the overview on the changing nature of urban environmental problems embedded in the spatial expansion of recent metropolitan area in Asia, along with exploring possible solutions from planning practices guiding sustainable urban development in Asia.