This study examines the economic role of environmental industries in the major Association of Southeast Asian Nations (ASEAN) economies using the environmental input-output (EIO) framework and multiregional input-output (MRIO) tables provided by the Asian Development Bank (ADB). It evaluates the production-inducement effects, value-added inducement effects, and inter-industry linkage structures of environmental industries in the five ASEAN countries: Indonesia, Malaysia, the Philippines, Thailand, and Vietnam. The results reveal three main findings. First, infrastructure-related environmental sectors, particularly the electricity, gas, and water supply sectors, exhibit strong inter-industry linkages and generate substantial production spillover effects across the ASEAN economies. Second, significant cross-country heterogeneity exists in value-added inducement effects, reflecting differences in industrial maturity, domestic value-chain depth, and institutional capacity. Third, the economic effectiveness of environmental industries depends not only on their scale, but also on their structural integration within national and global production networks. These findings suggest that environmental industries in ASEAN function not only as environmental management tools, but also as strategic drivers of economic growth.