Background: While low self-esteem is an established risk factor for depressive and anxiety disorders, psychological underpinnings of unstable self-esteem remain understudied. We investigated the role of autonomy-connectedness, the psychological capacity for self-governance, in self-esteem and its change trajectories and instability. Methods: Data spanning 12 years of the Longitudinal Internet studies for the Social Sciences [LISS] panel, a large, nationally representative population sample ( Results: Mixed model analyses revealed that autonomy-connectedness was positively associated with self-esteem. Autonomy-connectedness component Sensitivity to others predicted less deterioration of self-esteem over time. Latent growth mixture modeling exploring individual differences revealed seven latent classes differing in slope and self-esteem instability over time. Individuals with healthy autonomy were more likely to belong to classes with above average self-esteem, but not necessarily more stable self-esteem trajectories. A subgroup (11%) displayed alarming autonomy deficits, which corresponded with low, stable self-esteem, as well as high levels of depressive and anxiety symptoms. Conclusions: Autonomous individuals have higher self-esteem and better mental health, but autonomy deficits were not necessarily associated with Supplementary Information: The online version contains supplementary material available at 10.1007/s10608-025-10604-2.