OBJECTIVES: To elucidate the importance of mutual effects within dyads by examining the contribution of depression on quality of life (QOL) in patients with advanced cancer and their family caregivers (FCs). SAMPLE & SET TING : 716 patients with advanced cancer paired with their FCs at two large, private not-for-profit hospices. METHODS & VARIABLES: A descriptive, cross-sectional design with the baseline data of a randomized hospice clinical trial was used. Structural equation modeling helped examine four hypotheses by integrating the features of the Actor-Partner Interdependence Model. Variables included QOL and depression. RESULTS: Depression in patients with cancer and their FCs exhibited significant actor effects on an individual's QOL after controlling for the partner effects. Among the spousal pairs, depression in FCs exhibited a positive partner effect on the functional well-being of patients with cancer, indicating that depressive symptoms occurring in FCs may increase patients' functional well-being. IMPLICATIONS FOR NURSING: This study suggests the importance of consistent assessment in emotional well-being for dyads with cancer because their concerns may be transmitted to each other.