Aim: The purpose of this paper is to conceptually define "caregiver willingness" for application to a family member providing care to a critically ill loved one during an intensive care unit (ICU) hospitalization. Background: Delivering care to a family member may have psychological benefits for both the caregiver and the critically ill loved one; however, the willingness of family members to provide care is an elusive concept. Examination of the "caregiver willingness" concept will help to advance nursing science. Design: Walker and Avant's eight step strategy guided identification of the defining attributes, empirical referents, antecedents, and consequences of "caregiver willingness." Data Source: Academic Search Complete, CINAHL, MEDLINE, APA PsycInfo, and Psychology and Behavioral Health Collections were used to search for literature published between 2000 and 2020. Review Methods: A literature search was conducted using keywords, such as "caregiver," "willingness," "willing to care," "family or families or relatives or siblings or caregiver," and "critically ill or intensive care or ICU or critical care." Results: A definition of caregiver willingness was constructed and defined as "a family member or significant other's affirmation or acknowledgment of openness to engage in the physical and/or emotional supportive care of a loved one who is critically ill and cannot perform self‐care." Conclusion: The definition provides a foundation for instrument development to measure caregiver willingness and possible theory expansion for family engagement and caregiving in the ICU.