Substantial evidence linking family functioning to its members’ well-being and health outcomes has accumulated over the past several decades. Five essential health functions of the family include (1) development of members’ sense of personal identity and self-worth as a foundation for mental health, (2) socialization of family members to value and maintain practices that optimize health, (3) emotional sustenance and guidance during life cycle transitions, (4) education about when and how to use the health care system, and (5) care provision and management for chronically ill, disabled, and aging family members. This entry provides an overview of the family as a biopsychosocial system and illustrates how such knowledge may be used by health professionals to assess how well a family is meeting its health functions.