This investigation examined the importance of underlying motivations in predicting secure base support behavior, as well as the extent to which support motivations are predicted by individual differences in attachment orientation. Participants were 189 married couples who participated in two laboratory sessions. During a questionnaire session, couples completed assessments of their underlying motivations for providing, and for not providing, support for their partner's exploration (i.e., goal-strivings), as well as assessments of their typical secure base support behavior. In an observational session, couples engaged in a discussion of one member's personal goals, during which the partner's secure base support was assessed. Results revealed a variety of distinct motivations for providing, and for not providing, secure base support to one's partner, as well as theoretically expected links between these motivations and both secure base behavior and attachment orientation. This work establishes motivations as important mechanisms that underlie the effective or ineffective provision of relational support.