question: BACKGROUND: Social isolation encompasses subjective and objective concepts. Both are associated with negative health consequences and are more prevalent among people with mental health problems than among the general population. To alleviate social isolation, digital interventions have potential as accessible alternatives or adjuncts to face-to-face interventions. This scoping review aimed to describe the types of digital interventions evaluated for feasibility, acceptability and effectiveness in alleviating social isolation among individuals with mental health problems, and to present an overview of the quantitative evidence yielded to inform future intervention design. METHODS: We searched five electronic databases for quantitative and mixed methods studies published between January 2000 and July 2020. Studies were included if they evaluated digital interventions for individuals with mental health conditions, had subjective and/or objective social isolation as their primary outcome, or as one of their outcomes if no primary outcome was specified. Feasibility studies were included if feasibility outcomes were the primary outcomes and social isolation was among their secondary outcomes. A narrative synthesis was conducted to present our findings. The protocol was registered on Open Science Framework (doi:10.17605/OSF.IO/CNX8A). RESULTS: Thirty-two studies were included for our review: 16 feasibility studies, seven single-group studies and nine effectiveness trials. There was great variation in the interventions, study designs and sample populations. Interventions included web-based programmes, phone-based programmes, blended interventions, socially assistive robots and virtual reality interventions. Many were feasibility studies, or otherwise not fully powered to detect an effect if one were present, thus preventing clear conclusions about clinical effectiveness. Satisfactory feasibility outcomes indicated potential for future trials to assess these interventions. CONCLUSION: Our scoping review identified a range of digital approaches utilized to alleviate social isolation among individuals with mental health disorders. Conclusions regarding clinical effectiveness cannot be reached due to variability of approaches and lack of large-scale randomized controlled trials. To make clear recommendations for digital social isolation interventions, future research needs to be based on rigorous methods and larger samples. Future studies should also focus on utilizing theory-driven approaches and improving existing approaches to advance the field. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12888-022-03889-0.