Purpose: Cancer and its treatment can affect quality of life (QOL) in cancer patient and family caregiver dyads. However, the factors influencing dyad QOL remain inconclusive. Our study was designed to (i) assess dyads’ QOL, and examine the relationship between the QOL of cancer patients and that of their family caregivers, and (ii) investigate factors that may modify this relationship. Methods: Participants comprised 641 cancer patient-family caregiver dyads.