Almost one out of six older adults (≥ 65 years) suffers from poor mental health and this is even higher among older adults with a low socio-economic status (SES). Mental health is determined by individual and environmental factors. The physical environment (e.g., presence of greenery, pedestrian infrastructure, traffic safety) is particularly relevant for older adults’ mental health and even more so for older adults with a low SES. However, research on the relationships between physical environmental factors and older adults’ mental health is limited. Therefore, this project will apply innovative methods to examine the chronic and acute relationships between physical environmental factors and mental health among older adults, with a particular focus on older adults with a low SES. Secondary data analyses will be used to examine the chronic relationships between physical environmental factors and mental health. Mobile electroencephalography will be used to measure electrical activity of the brain when older adults walk through their neighbourhood. This enables to examine how physical environmental factors relate to acute changes in older adults’ emotional states such as relaxation and excitement. In addition, we will examine how changes to a 3D virtual environment influence older adults’ emotional states. The project will yield important information about how environments should be designed to optimally promote mental health among older adults in an equitable manner.