The proportion of UK employees who are part-time, temporary, agency staff, on zero hours contracts or self-employed has increased since PH22 was published in 2009. The Stevenson/Farmer review ‘Thriving at work’ estimates that 15% of UK workers have an existing mental health condition. Better mental wellbeing and job satisfaction are associated with increased workplace performance and productivity (Department for Business Innovation & Skills 2014). However, many employers know the value of positive mental wellbeing but do not know how to promote it. Therefore, the objective of this review is to identify targeted interventions at individual level for employees who are experiencing or who are identified as being at risk of poor mental wellbeing at work that are effective and cost-effective at: Preventing poor mental wellbeing. Promoting positive mental wellbeing. Improving mental wellbeing. Additionally, the review aims to determine the acceptability of these interventions for those receiving them, employers, and those delivering the interventions as well as any barriers and facilitators.