Background: Occupational eMental Health covers a wide variety of interventions using the potential of information and communication technology for the purpose of prevention and health promotion in employees. Based on extensive research in psychotherapy, internet-based interventions are increasingly being developed for chronically stressed employees. Objectives: To review the evidence on the efficacy of internet-based interventions for the promotion of mental health in teachers. Methods: A systematic literature search and meta-analysis on randomized controlled trials were conducted. Results: A total of 4155 abstracts were screened and four were included in the meta-analysis. Internet-based interventions led to a reduction in depressive symptoms (d = 0.68), improved quality of sleep (d = 1.03), reduced perseverative thinking in terms of improved mental detachment (d = 0.76), and reduced worrying (d = 0.60) compared with nonactive control groups. After 6 months, the effects for depression (d = 0.75), insomnia (d = 0.96), mental detachment (d = 0.83), and worrying (d = 0.63) remained stable. The effects for absenteeism were d = 0.18 (4.9 days) and for presenteeism d = 0.15 (4.3 days). Conclusion: Internet-based interventions are an effective and sustainable method for mental health preservation in teachers. They have the potential to reach target groups that have not been reached before by established interventions. The effects are similar to those observed for established interventions. More evidence from replication studies is needed, especially in the area of universal prevention and routine care.