Background: Burnout is significantly high among helping professionals and poses serious risks to one’s mental and physical health. Despite the high stress of environmental activists’ work and the importance of their role, there is little research on their mental health. Environmental activists protect the mental and physical health of the general population by advocating for environmental justice, pushing for large-scale changes to impede climate change, and providing education and resources for communities to navigate climate change-related events. This preliminary study aimed to contribute to the literature by gathering more information about burnout among environmental activists. Methods: A mixed methods framework employed a quantitative survey and qualitative individual interviews to ascertain the rates and experience of burnout from the point of view of the activists themselves. Activists were recruited from organizations throughout New York State that focus on climate change, climate justice, and environmental justice in community settings. Burnout, the main dependent variable, was measured with the Maslach Burnout Inventory. Independent variables included psychological distress, climate change-related anxiety, perceived organizational support, a variety of psychosocial workplace factors, and styles of coping. Correlation analyses were used to assess the relationship between burnout mean scores and mean scores on each of the independent variables. Qualitative interview data were analyzed by inductive Thematic Analysis and findings were organized and presented with the additional use of Consensual Qualitative Research (CQR) frequency methods. Results: Thirty-two participants completed the survey and eight activists agreed to subsequently complete the qualitative interview. Quantitative scales showed moderate burnout comprised of high emotional exhaustion and decreased feelings of accomplishment, and low depersonalization. Psychological distress was generally mild and climate change anxiety was high, but not impairing. Activists rated perceived organizational support as high and workplace factors as satisfactory. Emotional exhaustion was positively correlated with psychological distress and demands at work, and negatively correlated with perceived organizational support, interpersonal relationships and leadership, social capital, and health and wellbeing. Feelings of personal accomplishment were positively correlated with work organization and job contents, interpersonal relationships and leadership, and adaptive coping styles, specifically the use of emotional support, use of institutional support, and planning. Depersonalization was positively correlated with maladaptive coping styles involving denial, behavioral disengagement, and self-blame. The qualitative study interviews identified eight thematic areas associated with the experience of burnout, risk and protective factors, and factors unique to activism, activism and personal identity, and activism and current events. Qualitative outcomes aligned with quantitative outcomes, clarifying motivations for engaging in activism and experience of activism. Conclusions: This exploratory study helps illuminate important factors relevant to environmental activists’ mental health and offers recommendations for future research and mental health organizational policies. Future studies are needed with greater sample size, systematic sampling, and multiple assessment points, to better determine predictive relationships between these variables and burnout.