Background: Self-care systems for early-stage specialist palliative care for cancer patients and their family caregivers have received much attention recently. Resonant breathing is an established method for maximizing heart rate variability (HRV), but it has not been implemented for home self-care. Objective: We aimed to examine the usefulness and ease of implementation for family caregivers to administer resonant breathing using a portable device at home. Design: We divided caregivers into two groups—a home self-care group and a control group—and we conducted a randomized open-label study, with rate of change in HRV being the primary outcome. Setting/Subjects: We administered HRV biofeedback (HRV-BF) using resonant breathing to 54 family caregivers who felt burdened by their nursing care responsibilities. Results: Among the self-care group, 92.6% of participants completed the study in their homes; 28 days after intervention initiation, the resonant breathing implementation rate at home was 86.1%. There was an interaction between time course and grouping in our HRV comparisons: the change rate in the home self-care group was higher during HRV-BF than before HRV-BF. Conclusions: Because family caregivers in our study learned to quickly administer resonant breathing using a portable device at home, resonant breathing improved rapidly, along with autonomic nerve function and quality of life.