The informal caregiver experience has surged as a research topic in health care, including in nursing. However, the “informal” language is controversial, lacking conceptual clarity. Without a common understanding of who an “informal caregiver” may be, nurses may fail to consistently identify informal caregivers requiring support. Therefore, a concept analysis of “informal caregiver” was conducted on the basis of a sample of 20% of relevant nursing literature. The analysis of the attributes, antecedents, consequences, and contexts associated with “informal caregiver” offers a foundational guide for the ongoing development of nurses' understanding of the informal caregiver role.