ObjectiveCancer patients and their family caregivers often report elevated levels of depressive symptoms, along with poorer mental and physical health (quality of life: QOL). Although the mutuality in distress between patients and their caregivers is relatively well known, unknown are the degree to which caregivers' depressive symptoms independently predict their patient's QOL and vice versa, and whether the relations vary by cancer type or gender. MethodsColorectal or lung cancer patients and their caregivers (398 dyads) provided complete data for study variables (212 colorectal cancer patient dyads, 186 lung cancer patient dyads; 257 male patient dyads, 141 female patient dyads). Patients' depressive symptoms and QOL were measured approximately 4 and 12 months post‐diagnosis; caregivers' depressive symptoms and QOL were measured approximately 5 months post‐diagnosis. ResultsThe actor–partner interdependence model confirmed that each person's depressive symptom level was uniquely associated with his/her own concurrent QOL. Female patients' depressive symptoms were also related to their caregivers' poorer physical and better mental health, particularly when the pair's depressive symptoms were at similarly elevated level. On the other hand, male patients' elevated depressive symptoms were related to their caregivers' poorer mental health. ConclusionsFindings suggest that QOL among patients and their family caregivers is interdependent. In light of this interdependency, psychosocial interventions for managing depressive symptoms should target both patients and their family caregivers, from which both may benefit by not only alleviating depressive symptoms but also improving QOL. Copyright © 2014 John Wiley & Sons, Ltd.