This research tested whether and how partners' support of self-improvement efforts influences recipients' relationship evaluations and self-improvement success. Study 1 provided an initial test of predictions using self-reports (N = 150). Study 2 assessed support behavior exhibited in couples' (N = 47) discussions of self-improvement desires, and tracked relationship quality and self-improvement every 3 months for 1 year. More nurturing and action-facilitating partner support was more helpful to recipients, whereas partners who criticized and invalidated recipients were less helpful. Receiving more help from the partner, in turn, predicted greater relationship quality and more self-improvement. More negative support seeking also predicted lower self-improvement because recipients' behavior elicited less partner help. These effects were not attributable to partners' general warmth and understanding, global self or relationship evaluations, how much recipients desired or tried to change, or whether targeted attributes posed relationship problems. This research documents the powerful influence that partners' help has on recipients' personal growth.