The impact of lighting in buildings on managing behavioural and psychological symptoms, particularly in older adults, is significant as it affects visual and circadian systems. With age-related changes in eyes and circadian system, specialized lighting design is crucial to promote mood and overall well-being in older people. This study aimed to assess the effects of two types of ambient lighting interventions on depression in older adults. Both interventions involved creating a direct/indirect ambient illumination with high illuminance level (500 lux) in the morning (8:00-12:00), followed by gradual dimming throughout the day until reaching 100 lux in the evening (after 20:00). Depression levels were measured before, during, and after the lighting interventions using the Geriatric Depression Scale. The results showed a significant decrease in depression after exposure to both lighting conditions, with greater reduction observed in the L2 intervention. These findings highlight the positive effects of incorporating varying illumination and spectrum in the ambient lighting quality of residential buildings. Considering that older adults spend most of their time indoors, designing ambient lighting with varying intensity and tuning spectrum throughout the day could be a promising therapeutic approach to reduce depression, create an environment that promotes mental health, and improve the overall quality of life in older adults.