Existing literature on the relationship between urban green space (UGS) use and mental health of older people was mainly conducted before the widespread adoption of digital technologies in daily life. In particular, the COVID-19 pandemic outbreak has fostered the use of mobile applications (apps) at a time city dwellers, including older people, were required to stay home. Drawing upon the insights from emerging literature on the changing relationship between UGS use and mental health of older people in the digital era in urban and gerontological studies, this paper offers a vivid mixed-method to investigate whether mobile app use has supplemented or substituted UGS visits and activities that further influence on the mental health of older people. This is achieved by conducting 360 questionnaire surveys in elderly community centers amid the pandemic and 23 semi-structured interviews in local neighbourhood parks after the pandemic by the authors. Results demonstrates mobile app use frequency may moderate the proximity-mental health relationship, but only among the older people with lower mental health levels. Among this sub-group, digital consumption app use frequency weakens the proximity-mental health relationship on marginal significance, which illustrates digital consumption apps may substitute the role of urban parks on improving older people’s mental health. Furthermore, digital communication and recreation mobile app use frequency strengthens the proximity-mental health relationship on marginal significance, which suggests these mobile apps may supplement the role of urban parks on improving older people’s mental health, particularly during the pandemic. The research pleas for more research on how digitalization of everyday activities is transforming the use of UGS such as neighbourhood parks and subsequent impact on the mental health of older people in the widespread adoption of digital technologies.