BACKGROUND: A previous systematic review reporting the contributions of informal, unpaid caregivers to patient heart failure (HF) self-care requires updating to better inform research, practice, and policy. OBJECTIVE: The aim of this study was to provide an updated review answering the questions: (1) What specific activities do informal caregivers of adults with HF take part in related to HF self-care? (2) Have the activities that informal caregivers of adults with HF take part in related to HF self-care changed over time? (3) What are the gaps in the science? METHODS: This review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed, CINAHL, EMBASE, and Cochrane CENTRAL databases were searched. Eligible studies involved an informal, unpaid caregiver of an adult with HF as a study variable or participant. Caregiving activities were benchmarked using the theory of self-care in chronic illness. RESULTS: Two thousand one hundred fifty-four research reports were identified, of which 64 met criteria. Caregivers contributions occurred in self-care maintenance (91%), monitoring (54%), and management (46%). Activities performed directly on or to the patient were reported more frequently than activities performed for the patient. Change over time involved the 3 domains differentially. Gaps include ambiguous self-care activity descriptions, inadequate caregiving time quantification, and underrepresented self-care monitoring, supportive, and communication activities. CONCLUSIONS: Newly identified caregiver-reported activities support updating the theory of self-care in chronic illness to include activities currently considered ancillary to HF self-care. Identified gaps highlight the need to define specific caregiving activities, determine task difficulty and burden, and identify caregiver self-care strategy and education needs. Exposing the hidden work of caregiving is essential to inform policy and practice.