In two studies the authors examined whether self-concealment from one's partner is associated with lower relationship wellbeing. In Study 1, participants who were in a romantic relationship (N = 165) completed an online survey. Self-concealment from one's partner was associated with lower relationship satisfaction and commitment. Furthermore, results were consistent with this relationship being mediated by autonomy and relatedness needs. In Study 2, couples (N = 50) completed daily records for 14 consecutive days. Multilevel analyses indicated that daily self-concealment from one's partner was associated with daily relationship satisfaction, commitment, and conflict. Lagged analyses also showed that self-concealment from one's partner predicted lower relationship well-being on the following day. Moreover, results supported that thwarted basic needs mediated the association between daily self-concealment and relationship well-being. Finally, actor-partner interdependence model over time analyses indicated that, apart from one's own self-concealment, one's partner's self-concealment was associated negatively with one's own relationship well-being.