Objective: The objective of this study was to adapt and validate the Vietnamese version of Active Aging Index (AAI). Method: We conducted an expert panel, focus groups, test–retest and examination of internal consistency, and construct and concurrent validity among 804 older Vietnamese adults. Results: Scale content validity index (CVI) was 0.98. Test–retest coefficients ranged from 0.70 to 1.00. The Cronbach’s alphas of well-being, voluntary, affordability, and politics were 0.94, 0.70, 0.65, and 0.16, respectively. Voluntary and well-being had good construct validity. Regarding politics, only one of four items had good test–retest reliability (Kappa 0.84), while other three had low variance in both test–retest and field study. In exploratory factor analysis, items assessing affordability loaded on three components. AAI was positively associated with perceived health, life satisfaction, and quality of life; it was negatively associated with falls, loneliness, and frailty. Discussion: In adapting AAI, researchers should consider cultural sensitivity. Key modifications, findings, explanations, and suggestions are presented here.