Background: Providing informal care to persons with dementia (PWD) living at home can be challenging and lead to experience of caregiver stress and depression. Interventions delivered through mobile applications (apps) provide innovative solutions for community-based social care professionals to address the increasing support needs of family caregivers (FCs) to PWD. Objective: This study aimed to examine, among FCs to PWD living at home, a) the potential association between professional support provided through a mobile app and caregiver stress and depressive symptoms; b) types of support provided through chat interaction between FCs and social care professionals; c) how provision of support provided through a mobile app relates to changes in caregiver stress and depressive symptoms. Methods: A mixed-methods pilot study was conducted integrating quantitative pre- and post-intervention data and qualitative logged chat data. FCs to PWD living at home (n=35) were recruited to test a tailor-made mobile app over eight weeks. The outcome measures were caregiver stress (primary) and depressive symptoms (secondary). Descriptive statistics were used to describe socio-demographic factors. Inferential statistics were used to analyse mean differences in the outcome measures pre- and post-intervention. FCs were divided into three groups based on changes in caregiver stress scores between pre- and post-intervention. Generalized linear models (GLM) analyses were used to determine the association between participation in the intervention on caregiver stress and depressive symptoms, controlling for age, gender and relationship to the PWD. Logged chat data was analysed using summative content analysis to identify types of support provided and received. Changes in caregiver stress were integrated with the chat data to determine patterns in the types of support received. Results: The mean age of the FCs was (69.4), with most being women (80%), partners (68.6%) and living together with the PWD (74%). The mean score of FCs' caregiver stress was marginally higher post-intervention (24.1, SD 9.3) compared to pre-intervention (23.9, SD 9.2), while the mean score of their depressive symptoms declined between pre- (6.5, SD 5.1) and post-intervention (6.2, SD 5.2). These differences were not statistically significant. Regression analyses showed that participation in the intervention was not statistically significantly associated with caregiver stress (β=0.171, α=.05, P=.862) or depressive symptoms (β= -0.293, α=.05, P=.745) after adjusting for age, gender and relationship to the PWD. However, mixed-methods analysis at the sub-group level, suggests that frequently provided tailored support by social care professionals delivered through a mobile app potentially can reduce caregiver stress among FCs to PWD living at home. Conclusions: The study highlights the importance of providing frequent and tailor-made support to meet the individual needs of FCs to PWD. The findings from this study can help community-based social care providers plan and organize the content of digital support provided for FCs to PWD living at home.