Research on environmental activism remains poorly integrated and ill-defined and to date, there has been little examination of the relationship of environmental activism, pro-environmental behaviour and social identity. 131 students from an Australian University (M = 25.04 years old, SD = 8.17) voluntarily participated by returning an anonymous questionnaire containing an environmental activism scale, a pro-environmental behaviour scale and a social identity scale. The results revealed that while there was a significant relationship between social identity and environmental behaviour, only the citizenship component of environmental behaviour significantly predicted environmental activism. In other words, the relationship between social identity and environmental activism was indirect. This research presents the opportunity for further exploration of these relationships and to further investigate their relationship to inter-group processes.