This study lies in the burgeoning literature on the contextual effects of the adoption of mobile applications (apps) on the everyday lives and integration of older migrants into a host society, taking the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in South China as a case. Despite recent advocacy of healthy ageing and regional integration, most GBA studies related to cross-border ageing have focused on welfare portability instead of the everyday life adaptation of older migrants through use of digital technologies. This article investigates and compares how mobile apps have facilitated/hindered the integration of Hong Kong older migrants in Shenzhen, through a comparative investigation of mobile app adoption between Hong Kong older migrants and local Shenzhen older adults. A mixed-method approach is adopted including focus group meetings with Hong Kong older migrants living in Shenzhen, and questionnaire surveys with Shenzhen local older adults between September 2021 and March 2022. The study sheds light on two major findings. First, facing the highly digitalized Shenzhen, Hong Kong older migrants have caught up more with using instrumental apps (e.g. mobile payment), as compared with recreational, informational, and open (one-to-many) communication apps. Second, Hong Kong older migrants have emphasized the use of apps for cross-border interactions. The digital gaps in terms of different using patterns of mobile apps highlight Hong Kong older migrants’ lack of socio-cultural integration and feeling of separation from the host society. This study advocates for more active involvement of older migrants’ specific needs in designing mobile apps. Multi-scalar cooperation among various localities in the GBA region is deemed important for older migrants to further integrate into the host society with the widespread use of digital technologies in everyday life.