Since NICE guideline PH22 Mental wellbeing at work was published in 2009, the nature of the workforce has changed in the UK. Increasing amounts of employees are on part-time, temporary, or zero-hours contracts. The variations between workplaces and differences in the nature of employment are important to consider when looking at approaches to improve and protect employee mental wellbeing. Since 2009 there has been increasing recognition of mental wellbeing and how it is associated with the workplace and work outcomes. The Stevenson/Farmer review ‘Thriving at work’ estimates that 15% of UK workers have an existing mental health condition, and experiences in the workplace can affect mental wellbeing positively and negatively. Good employee mental wellbeing is positive for employees and their employers. Better mental wellbeing and job satisfaction are associated with increased workplace performance and productivity (Department for Business Innovation & Skills 2014). Poorer mental wellbeing however is associated with increased absenteeism and presenteeism and lost output costs the economy upwards of £74 billion annually. It is therefore important to implement interventions in the workplace to promote and improve mental wellbeing, and to prevent poor mental wellbeing amongst the workforces. Many employers know the value of positive mental wellbeing but do not know how to promote it. Understanding what approaches are effective in preventing poor mental wellbeing, as well as promoting and improving mental wellbeing in the workplace are important, but of equal importance is understanding the barriers and facilitators to implementing and delivering mental wellbeing interventions, programmes, policies, or strategies at work.