Purpose : This study examines South Korea's evolving investment treaty strategy, tracing the transition from early Bilateral Investment Treaties (BITs) toward prospective accession to the CPTPP, within the broader context of Indo-Pacific economic integration. Research design, data, methodology : The study employs a qualitative approach integrating treaty text analysis, policy document review, and comparative analysis, contrasting Korea's investment governance trajectory with that of Japan, Australia, and Singapore. International political economy frameworks are applied to identify underlying strategic motivations. Results : Korea's investment treaty strategy has shifted from a passive, bilateralism-centered approach to a proactive multi-layered model that links trade, digital economy, and sustainability norms. This shift reflects Korea's recalibration in response to shifting Indo-Pacific power dynamics and the demand for deeper institutional integration. Conclusions : Korea's prospective CPTPP accession strategy represents a strategic repositioning in investment governance, bridging economic openness with national interest and resilience. Medium-sized economies like Korea must navigate the tension between normative alignment and domestic structural adjustment when engaging in mega-regional investment frameworks.