This study was designed as an intervention study to determine the effect of light therapy on sleep problems and sleep quality of elderly people. The study sample was composed of a total of 61 elderly persons from Social Security Institution Narlidere Municipal Nursing Home, 30 in the test group and 31 in the control group. Those 65 years and older, not diagnosed with major depression, not exercising regularly, not having sun allergy, not using sleeping pills, independent in activities of daily living, and having bad sleep quality were included in the study. The Pittsburgh Sleep Quality Index, the Demographic Data Form, and the Follow-up Form for Elderly were used for data collection, whereas the Pittsburgh Sleep Quality Index was used for sample selection. It was found that exposure to direct sunlight between 8 AM and 10 AM for 5 days seems to be effective in increasing the global sleep quality score (P<.001). In light of the findings in this study, it is suggested that allocating living places in the institution's architectural setting and providing social opportunities for elderly persons to get direct sunlight exposure can help increase the sleep quality of older adults.