Events are a growing sector, often attracting tourists to destinations. There is increased emphasis on achieving sustainability in event management; some festivals, particularly large outdoor music festivals, are leading in greening their events. This paper explores the drivers of, and barriers to, greening festivals and considers how events might be a vehicle for promoting sustainable behaviour. The application of the Mair and Jago model is tested. Long interviews were conducted with managers of six UK and Australian festivals that have won awards for their green performance and an organisation that encourages the greening of festivals. Findings suggest that managers of these festivals act both as a champion and a steward of greening and that the key drivers of festival greening are the personal values or ethos of the manager and/or the organisation, demand for greening from stakeholders and a desire to educate and act as an advocate of green issues. Barriers to greening festivals included the financial costs, lack of time and control over festival venues and the inability to source appropriate suppliers or supplies. Further research could explore these issues in other events contexts and examine whether events leave a lasting legacy in terms of influencing environmental behaviour.