<![CDATA[The Indonesia–Malaysia border region is a dynamic space where cross-border migration creates economic opportunities while increasing the demographic-economic vulnerability of local communities. This study examines the interrelationships among migration geodynamics, demographic-economic vulnerability, and social resilience in Nunukan Regency, North Kalimantan Province, and formulates directions for integrated border development policies. The study covered mainland Nunukan, Sebatik Island, the former Simantipal Outstanding Boundary Problem (OBP) area, and the Sinapad Sesai segment. A qualitative approach supported by descriptive-quantitative secondary data was employed within a Grounded Policy Research framework. Data were collected through field observations, document analysis, and in-depth interviews with 17 purposively selected key informants: seven migrant workers, three migrant families, two community leaders, and five government officials. Data were analyzed using the Spradley Ethnographic Analysis Model. The findings show that high population mobility and strong economic linkages with Sabah, Malaysia, have increased dependence on informal economic activities, cross-border markets, and employment opportunities in Malaysia, contributing to structural demographic-economic vulnerability. Nevertheless, communities demonstrate social resilience through livelihood diversification, strengthened social capital, and adaptive population administration. The study concludes that integrated border development should prioritize local economic strengthening, downstream seaweed processing, and the strengthening of the Tol Laut (Sea Toll) logistics system, supported by improved population administration and cross-border governance. These interventions can reduce economic dependence on Malaysia, strengthen local economic self-reliance and social resilience, and position Nunukan as an economic shield that supports community welfare and national sovereignty]]>
