Background: During the COVID-19 pandemic, healthcare providers and informal caregivers were at an increased risk of adverse mental health effects. This systematic review provides a summary of the available evidence on the content and efficacy of the psychological support interventions in increasing mental health among healthcare providers and informal caregivers during the COVID-19 pandemic. Methods: PubMed, Google Scholar, PsychINFO, and Scopus databases were systematically searched for relevant articles, and the methodological quality of selected articles was assessed using the Quality Assessment Tool for Quantitative Studies. Results: A search of electronic databases identified five reports based on inclusion and exclusion criteria. All psychological support interventions for caregivers were delivered digitally. Despite the large heterogeneity of the selected studies, the findings support the efficacy of mental health interventions in reducing distress and burnout, while promoting self-efficacy and well-being in both healthcare providers and informal caregivers. Conclusion: Since mental health problems are expected to increase during, and as a result of, the COVID-19 pandemic, and digital tools might offer a range of mental health treatments to meet the unique and immediate needs of people, further research is needed to test the cost-effectiveness of digital psychological interventions.