["Applied Psychology: Health and Well-Being, Volume 18, Issue 4, August 2026. ", "\nAbstract\nThe role of identity content in adolescent subjective well‐being (SWB) is poorly understood. To address this gap, the present longitudinal study examined the relationships between two dimensions of interdependent self‐construal (relational and collective) and SWB (positive affect, negative affect, and life satisfaction). We also investigated whether basic psychological needs satisfaction could serve as a mechanism explaining the relationship between interdependent self‐construal and SWB. The sample consisted of 971 Serbian adolescents (Mage = 15.64, 64.5% female), who completed surveys at three time points over a 12‐month period. The results of random intercept cross‐lagged panel modeling indicated that: (1) adolescents reporting consistently higher levels of collective self‐construal also reported consistently higher levels of SWB, whereas adolescents reporting consistently higher levels of relational self‐construal showed consistently higher positive affect but neither higher life satisfaction nor lower negative affect; (2) within‐person deviations in interdependent self‐construal were not associated with subsequent deviations in SWB; and (3) the satisfaction of basic psychological needs did not mediate the association between interdependent self‐construal and SWB at the within‐person level. Overall, the findings suggest that the relationship between interdependent self‐construal and SWB operates primarily at the between‐person level rather than the within‐person level, indicating that stable patterns of self‐definition are more strongly related to adolescents' well‐being than within‐person changes in self‐definitions over the one‐year study period.\n"]