Understanding undergraduates’ environmental behaviour is important as they will be the leaders of the country in the near future. They play an important role in protecting and conserving the environment. This paper investigates the undergraduates’ behaviours towards the environment after completing the Environment Economics course. Theory of Planned Behaviour (TPB) together with some other factors such as academic performance, government regulations and perceived importance of nature are employed. Multiple regression analysis shows undergraduates’ behaviours is positively affected by attitude and perceived importance of nature, and negatively influenced by government regulations. Although academic performance is very important to provide an understanding of basic principles of environmental sustainability, it however does not significantly influence their environmental behaviour. The finding hopes to assist the policy makers to plan future strategies so that the undergraduates behaviours can make a difference to nature and the environment