Although identifying as an environmentalist predicts one’s engagement in pro-environmental behaviour, the way in which outgroup members perceive environmentalists may contribute to whether an individual identifies with the group. Yet no research to date has explored the content of the stereotype outgroup members hold of the environmentalist social category. A qualitative survey was therefore conducted to obtain an in-depth understanding of how outgroup members describe and view environmentalists as a whole. Using Amazon Mechanical Turk, 89 US residents aged 21 to 53 (female = 37; Mage = 32.74, SDage = 7.89) who did not belong to any environmental organisations answered a series of open-ended questions concerning their perceptions of environmentalists. Data obtained were analysed using thematic analysis, with four themes identified across participants: (1) All environmentalists care about and value nature; (2) Environmentalists are active in protecting and conserving nature; (3) Most environmentalists are altruistic and self-sacrificing; and (4) Not all environmentalists are extreme and aggressive, but many act that way. Findings demonstrated that the outgroup stereotype of environmentalists contained both positive and negative components; environmentalists were seen to value the natural environment and to be actively involved in bringing about positive environmental change (the positive component), yet were also viewed as aggressive in their behaviours and stubborn in their beliefs (the negative component). These findings not only challenge the assumption that outgroup members typically evaluate environmentalists negatively, but also have implications for why some individuals may fail to identify as an environmentalist in the first place.