Background: Factors associated with sleep quality have not been well examined in hospitalized older persons with dementia, who are at high risk for impaired sleep. The aim was to identify factors associated with sleep quality among hospitalized persons with dementia. Methods: This secondary analysis used baseline data from a cluster randomized trial. Factors examined included delirium severity, pain, depression, behavioral and psychological symptoms of dementia (BPSD), and daytime physical activity. Multiple stepwise linear regressions evaluated factors related to dimensions of sleep quality (sleep duration, efficiency, latency, and fragmentation; measured by the MotionWatch 8). Results: Increased daytime physical activity was associated with higher sleep duration [β=0.164; 95% confidence interval (CI), 0.111-0.717; P=0.008; 7.7% variance] and sleep efficiency (β=0.158; 95% CI, 0.020-0.147; P=0.010; 5.4% variance), and less sleep fragmentation (β=-0.223; 95% CI, -0.251 to -0.077; P<0.001; 10.4% variance). Higher BPSD was significantly associated with prolonged sleep latency (β=0.130; 95% CI, 0.098-2.748; P=0.035; 3.7% variance). Conclusion: Results suggest the need to encourage daytime physical activity and reduce or manage BPSD to improve sleep quality among hospitalized persons with dementia.