Attachment orientations predict relationship outcomes and health and well-being, making it important to illuminate factors which enhance attachment security. We investigated how general and relationship-specific mindfulness predict changes in attachment orientations in couples over time, testing relationship preoccupation and partner-focused empathy as mediators. We also explored whether the longitudinal links between general mindfulness and attachment are bidirectional. Couples reported their general and relationship mindfulness and attachment orientations in a baseline session (Phase 1). They then reported relationship preoccupation and empathy each day for 14 days (Phase 2). Lastly, they reported general mindfulness and attachment orientations 2 months later (Phase 3). Results revealed that higher Phase 1 actor general—but not relationship—mindfulness directly predicted Phase 1-3 decreases in actor attachment anxiety. Conversely, greater Phase 1 actor relationship—but not general—mindfulness indirectly predicted Phase 1-3 decreases in actor attachment avoidance via greater Phase 2 actor empathy. Finally, lower Phase 1 actor and partner attachment anxiety directly predicted Phase 1-3 increases in general mindfulness. This research provides the first dyadic longitudinal demonstration of the interplay between partners’ mindfulness and attachment.