This secondary analysis examined whether the benefits of bright light therapy on depression are greater in persons with mild/moderate or severe dementia. Exploratory analyses were also conducted to determine if bright light treatment targets different depressive symptom clusters based on dementia severity. Analyses using total scores from the instruments, Depressive Symptom Assessment for Older Adults and the Cornell Scale for Depression in Dementia, showed that bright light exposure is an equally effective intervention for depression in persons with both mild/moderate and severe dementia. Analyses of individual depressive subscales revealed that for disagreeable behavior and sleep impairment, bright light therapy appears to have greater benefits in persons with severe dementia than for those with mild/moderate dementia. Overall, this investigation supports the use of bright light therapy to treat depression regardless of dementia severity.