T The development of coastal areas in the banten coastal region poses serious challenges to environmental sustainability and the welfare of coastal communities. the implementation of the strategic environmental assessment (sea) in coastal area development planning has not yet been optimal, despite the fact that this instrument is explicitly mandated under article 15 of law number 32 of 2009 concerning environmental protection and management.the main issues examined in this thesis are: (1) how the implementation of the strategic environmental assessment in the development of coastal areas in banten in 2024 is reviewed based on article 15 of law number 32 of 2009; and (2) what the juridical impacts of the strategic environmental assessment (sea) in coastal areas are if it is not implemented optimally.the research method applied is normative juridical research, employing statutory, conceptual, and case approaches. the results of the study indicate that the regulation of the strategic environmental assessment (sea) has been expressly stipulated; however, its implementation has not been carried out optimally. the juridical impact arising from such suboptimal implementation includes delays in the establishment of spatial planning documents, which should serve as the primary legal reference for controlling spatial utilization and determining the direction of provincial development in the medium and long term.