Social approaches can contribute to clarifying environmental issues. For instance, social identity theory can help to comprehend people's motivations for getting involved in environmental protection. However, the kind of social identity best suited for predicting environmental protection engagement remains unclear. This study examines different categories of social identity in relation to different types of environmental protection engagement. The predictive power of identification with environmentalists, as well as with politicized and non-politicized environmental groups, are considered separately. Furthermore, environmental protection engagement is divided into pro-environmental behavior and two different demanding forms of pro-environmental collective action—participatory environmental action and leadership environmental action. Data collected online from 985 respondents involved in environmental protection were analyzed using structural equation modeling. The results showed that while environmental group identification was not significantly related to any kind of environmental protection engagement, environmentalist identification emerged as a predictor of participatory environmental action, leadership environmental action and pro-environmental behavior. Moreover, these connections were stronger for participants belonging to a politicized environmental group than for those belonging to a non-politicized environmental group and those not belonging to any environmental group. These results support and extend previous findings on the role of social identity in pro-environmental collective action and pro-environmental behavior.