Background/Study context: The aim of the present work was to investigate the association of Waist-to-Height Ratio (WHtR) with Successful Aging (SA) status and compare it to classic anthropometric indices, among middle-aged and older individuals. Methods: Among various socio-demographic, clinical and lifestyle characteristics, height, weight, waist circumference (WC), Waist-to-Hip Ratio (WHR) and WHtR of the Greek participants, over 50 years old, enrolled in the ATTICA (n = 1,128) and the MEDIS (n = 2,221) in relation to SA; SA was evaluated using the validated Successful Aging Index (SAI, range 0–10) comprising of health-related, social, lifestyle, and clinical parameters. Results: WHtR was inversely associated with SAI with every 0.1-unit increase, lowering SAI by almost 0.5 units (b-coefficient±SE: −4.71 ± 0.26; 95%CI: −5.21, −4.20). Also, WHtR was more strongly associated with SAI (b = −0.352), surpassing the effect of age and sex (b = −0.347 and 0.11, respectively). With respect to the other anthropometric indices (weight, height, WC, WHR), WHtR exhibited the highest explanatory ability (Adjusted R2 = 0.345); the higher the adjusted R2 the higher explanatory ability. Conclusions: WHtR was revealed as the best determinant of successful aging, with respect to other anthropometric indices (weight, height, WC, WHR). The present findings are of significant public health importance for better understanding the role of body mass distribution on the aging process.