This study aims to evaluate the effect of light therapy on depression and sleep disruption in older adults residing in a long-term care facility. Psychological morbidity is a problem commonly seen in older adults residing in long-term care facilities. Limited research has addressed the effect of light therapy on depression in this population. A quasi-experimental pretest and posttest design was used. Thirty-four participants in the experimental group received light therapy by sitting in front of a 10000-lux light box 30 min in the morning, three times a week for 4 weeks. Thirty-one participants in the control group received routine care without light therapy. Depression was measured by Geriatric Depression Scale-Short Form at baseline and week 4. After receiving 4 weeks of light therapy, the mean depression score in the experimental group decreased from 7.24 (SD3.42) at pretest to 5.91 (SD 3.40) at posttest, and had a significant reduction (t = 2.22, P = 0.03). However, there was no significant difference in depression score and sleep disruption between the experimental group and control group. Light therapy might have the potential to reduce depressive symptoms and sleep disruption and may be a viable intervention to improve mental health of older adults in the long-term care facilities.