This study examines Vietnam's strategic deployment of sports diplomacy through the Southeast Asian Games (SEA Games) to facilitate its geopolitical transformation from regional isolation to middle power status. Drawing on Joseph Nye's soft power theoretical framework, the research traces Vietnam's SEA Games participation across four distinct historical phases: (i) Cold War participation as the Republic of Vietnam (1959-1975); (ii) post-unification absence during political isolation (1975-1989); (iii) strategic re-entry and gradual integration (1989-2003); and (iv) emergence as a regional sporting power (2004-present). Through historical analysis and inductive methodology, the study identifies four strategic pillars characterizing Vietnam's approach: (i) cultural integration through traditional sports; (ii) systematic credibility-building through improved performance; (iii) strategic exploitation of hosting opportunities for nation branding; and (iv) using sports as diplomatic bridges for relationship-building. The findings demonstrate what this study terms the “dialectical” relationship between sports and politics, illustrating how sporting engagement both reflects and actively shapes diplomatic relations and geopolitical standing. Vietnam's transformation from absent participant to regional sporting leader temporally correlates with its broader diplomatic evolution toward recognized middle power influence in Southeast Asia. This research addresses a critical gap in understanding how emerging middle powers in non-Western contexts deploy soft power through regional sporting platforms, offering applicable insights for other nations seeking to enhance regional influence through sports diplomacy strategies.