Background: Previous studies have documented cognitive impairments, psychological stress, and depressive symptoms in family caregivers of people with dementia (PWD), which could be attributed to their sleep disturbances. Notwithstanding the increasing recognition of poor sleep quality and sleep disturbances in family caregivers of PWD, their association has not been tested yet using population-representative samples. Methods: We conducted a retrospective, cross-sectional study using population-based data from the 2018 Korean Community Health Survey. Sociodemographic, mental health-related, and physical health-related variables as well as sleep quality evaluated by the Pittsburgh Sleep Quality Index (PSQI) were compared between 2537 cohabitating caregivers of PWD, 8864 noncohabitat-ing caregivers of PWD, and 190,278 non-caregivers. Two sets of multivariable logistic regressions were conducted to examine the associations between dementia caregiving and poor sleep quality in cohabitating and noncohabitating caregivers versus noncaregivers. Results: Both cohabitating and non-cohabitating caregivers had higher global PSQI scores and higher prevalence of poor sleep quality (PSQI score > 5) than did noncaregivers. Multivariable logistic regressions adjusted for potential confounders revealed that cohabitating caregivers (odds ratio (OR) 1.26, 95% confidence interval (CI) 1.15–1.38) and noncohabitating caregivers (OR 1.15, CI 1.10–1.21) were significantly associated with poor sleep quality. Conclusions: Our results showed that both cohabitating and noncohabitating caregivers of PWD experienced overall poorer sleep quality compared to noncaregivers, indicating the deleterious effect of dementia caregiving on sleep quality, regardless of living arrangements. Given the high prevalence of poor sleep quality in family caregivers of PWD and the increasing awareness of the serious health consequences of poor-quality sleep, physicians should consider active sleep interventions to promote health and wellbeing not only for the dementia patients but also for family caregivers.