Aim: Several studies have reported a negative correlation between depressive symptoms and family caregivers' (FCs) subjective sleep status. However, there is a paucity of information on the association between objective/subjective sleep status, care burden, and related factors.; Methods: Participants were 23 pairs of care receivers (CRs; Mage = 82.7 ± 8.5 years; 69.6% women) receiving long-term care at home and their FCs (Mage = 66.9 ± 11.0 years; 69.6% women). At baseline, demographic data, subjective sleep status (Pittsburgh Sleep Quality Index; PSQI), WHO-5 well-being, depressive mood, and frequency of going outdoors were collected. FCs wore a small, wrist-worn device with an accelerometer to assess objective sleep status for a consecutive 24-h 2-week period, and they answered the Zarit Burden Interview short version (ZBI) every night before sleep. After 3 months, CR status was collected and analysed retrospectively.; Results: The mean total sleep time over 2 weeks was 349.5 ± 69.6 min. The mean ZBI score over 2 weeks was 8.8 ± 6.8, which was significantly correlated with total sleep time (r = -0.42; P < 0.05), total time in bed (r = -0.44; P < 0.05), PSQI (r = 0.62; P < 0.01), frequency of going outdoors by CRs (r = -0.42; P < 0.05), and WHO-5 well-being among CRs (r = -0.50; P < 0.05). Multiple regression analyses revealed that total sleep time (β = -0.51; P < 0.05) was significantly associated with care burden (adjusted R2 = 0.45). At the 3-month follow-up, four CRs had been hospitalised or died, and their FCs displayed significantly severe care burden and slept less than at baseline.; Conclusions: Reduced objective total sleep time is significantly associated with the severity of care burden among FCs. Home-based care is critical in Japan; therefore, it is meaningful to determine how to reduce care burden.