Main Abstract Content: Background. There is growing interest in web-based intervention for promoting mental health in working populations. A number of randomized controlled trials have been conducted; however the results are heterogeneous. This work aims to synthesize the results of randomized controlled trials on web-based mental health interventions for employees. Methods. A systematic search was performed and 4151 abstracts were identified. A meta-analysis was conducted including 18 studies. Cohen’s d was calculated for stress and depression to estimate the effect of the intervention group compared with a care as usual-, a waitlist-, or a no-treatment control group. Results. Analysis of data is still on-going. Available results show small to moderate effect sizes for web-based mental health interventions in employees for the reduction of stress (Cohen’s d=0.43, 95% CI=-0.23-0.63, n=15) and depression (d=0.35, 95% CI =0.18-0.52, n=13). Interventions of medium length (4-8 weeks) are significantly more effective than long (≥ 9 weeks) and short (≤ 4 weeks) interventions in reducing stress (p<.001) and improving depressive symptoms (p<.05). Moreover, guided interventions are superior to unguided interventions in reducing stress and depression (p<.01). No significant difference was present for the type of treatment. Discussion. This meta-analysis demonstrates that internet interventions for improving mental health in employees are available and can be effective. However, the effect sizes of the trials vary from non-significant to large, indicating that each individual intervention needs to be evaluated before implementation. So far, the interventions are designed along theories of work-stress only seldom and moderators of chance are almost unknown. Disclosure of Interest: D. Lehr Conflict with: DL reported holding shares of the Institute for Online Health Training, which aims to transfer scientific knowledge related to the present research into routine mental health care in Germany., E. Heber: None Declared, D. Ebert Conflict with: DE reported holding shares of the Institute for Online Health Training, which aims to transfer scientific knowledge related to the present research into routine mental health care in Germany.