Feeling younger than one’s chronological age (i.e., a younger subjective age bias) has been consistently linked to better health, performance, and extended longevity. Yet, it is not clear whether there is a “right amount” of feeling younger that contributes to better well-being (e.g., “feeling younger but not too young”). Thus, we tested three key hypotheses about the adaptivity of subjective age bias across adulthood: (1) maintaining a younger subjective age is beneficial and indicates normal, well-adjusted well-being (positivity bias hypothesis); (2) there is an optimal margin for subjective age bias and maintaining a small positive distortion is the most beneficial for well-being (optimal margin hypothesis); (3) there is an optimal margin, but it increases as people get older (shifting optimal margin hypothesis). We used polynomial regression and response surface analyses to model these relationships between chronological age, subjective age, and subjective well-being on the basis of a large age-heterogeneous sample (English Longitudinal Study of Ageing, N = 7361; 36 – 89 years). Our results support that there is an optimal margin of subjective age bias: people who feel moderately younger than they actually are report the highest levels of life satisfaction, while people deviating from this optimal margin report lower levels of life satisfaction. In addition, our findings tentatively suggest that this optimal margin increases in older age groups.