OBJECTIVES: To examine relationships in mindfulness and illness acceptance and psychosocial functioning in patients with metastatic breast cancer and their family caregivers. SAMPLE & SETTING: 33 dyads from an academic cancer center in the United States. METHODS & VARIABLES: Participants completed questionnaires on mindfulness, illness acceptance, relationship quality, anxiety, and depressive symptoms. Dyadic, cross-sectional data were analyzed using actor-partner interdependence models.