["Japanese Psychological Research, EarlyView. ", "\nAbstract\nThis paper adds critical detail on the role of personality, specifically the impact of extraversion, to recent findings on the relationship between social support resources and well‐being. Based on previous studies showing personality differences in utilizing social capital, as well as in positive outcomes, such as well‐being, we assume that extraversion interacts with both. Referencing our previous research and cultural psychological findings on the “interdependence” of extraversion in the Japanese context, we also expect that the interaction is stronger for emic interdependent happiness than for etic life satisfaction. Using a Japanese well‐being survey (n = 2,500) and interaction analysis, the study confirms a significant moderating impact of extraversion on the association of social capital and well‐being. The findings suggest that introverts benefit more from additional support resources, while extraverts are maintaining a higher level of well‐being compared at every level of support. However, introverts with high levels of social support surpass extraverts with low levels of support in terms of well‐being. As predicted, the interaction is stronger for interdependent happiness, emphasizing potential cultural effects. Possible underlying mechanisms and implications are discussed.\n"]