Background: Stress, depression and anxiety amongst working populations can result in reduced work performance and increased absenteeism, but while there is evidence that these common mental health problems are preventable and treatable in the workplace, uptake of psychological treatments amongst the working population is low. One way to address this may be the delivery of occupational digital mental health interventions, but while there is convincing evidence for delivering digital psychological interventions within a health and community context, there is no systematic review or meta-analysis of these interventions in an occupational setting. Objective: This review aims to identify the effectiveness of occupational digital mental health interventions in enhancing employee psychological wellbeing and increasing work effectiveness, and to identify intervention features associated with the highest rates of engagement and adherence. Methods: A systematic review of the literature was conducted using Cochrane guidelines. Papers published between 2000 and May 2016 were searched in 2 the PsychINFO, MEDLINE, PubMed, Science Direct and the Cochrane databases, as well as the databases of the researchers and relevant websites. Unpublished data was sought using the Conference Proceedings Citation Index and the Clinical Trials and ISRCTN research registers. A metaanalysis was conducted by applying a random-effects model to assess the pooled effect size for psychological wellbeing and the work effectiveness outcomes. A positive deviance approach was used to identify those intervention features associated with the highest rates of engagement and adherence. Results: In total 21 RCTs met the search criteria. Occupational digital mental health interventions had a statistically significant effect post intervention on both psychological wellbeing (g = 0.37, 95% CI: 0.23 to 0.50) and work effectiveness (g = 0.25, 95% CI: 0.09 to 0.41) compared to the control condition. No statistically significant differences were found on either outcome between studies using CBT approaches (as defined by the authors) compared with other psychological approaches, offering guidance compared with selfguidance, or recruiting from a targeted workplace population compared with a universal workplace population. In depth analysis of the interventions identified by the positive deviance approach suggests that interventions that offer guidance, are delivered over a shorter timeframe (6 to 7 weeks), utilise secondary modalities for delivering the interventions and engaging users (i.e. emails and text messages), and use elements of persuasive technology (i.e. self-monitoring and tailoring) may achieve greater engagement and adherence. Conclusions: This review provides evidence that occupational digital mental health interventions can improve workers’ psychological wellbeing and increase work effectiveness. It identifies intervention characteristics that may increase engagement. Recommendations are made for future research, practice and intervention development. Registration: The protocol for this systematic review and meta-analysis was registered with the International Prospective Register of Systematic Reviews (PROSPERO; registration number CRD42016033935).