BACKGROUND: Nursing well-being has become a heightened focus since the COVID-19 pandemic. Nurses are leaving the profession early in their careers or retiring sooner than expected. Those who remain in the workforce report higher levels of burnout, anxiety, depression, and exhaustion. There is concern that there may be a shortage of at least half a million nurses by 2030. AIMS: This systematic review aimed to investigate the evidence of using a mental health promotion mHealth app to improve the mental health of hospital nurses. METHODS: A systematic search was conducted in CINAHL Plus with Full Text, MEDLINE with Full Text, Professional Development Collection, Psychology and Behavioral Sciences Collection, Sociological Collection, PsycInfo, Embase, and PubMed with search dates of January 2012-November 15, 2022. The mHealth intervention needed to be asynchronously delivered through a smartphone with hospital nurse participants to be included in this review. RESULTS: Of the 157 articles screened for this review, six were included. Primary outcome variables were anxiety, burnout, coping, depression, self-efficacy, stress, well-being, and work engagement. Intervention types included mindfulness-based interventions (MBIs), cognitive behavioral therapy (CBT), stress inoculation therapy (SIT), psychoeducation, and stress management. Anxiety, depression, well-being, and burnout improved with MBIs; depression improved with CBT; and anxiety and active coping improved with SIT. LINKING EVIDENCE TO ACTION: This review demonstrated promising findings in using mHealth apps to improve the mental health of hospital nurses. However, more randomized controlled trials with larger sample sizes may reveal which type of mHealth app and how much exposure to the intervention is more effective in improving specific mental health symptoms. Longitudinal follow-up is also recommended to study sustainability of the mental health improvements.