This study examines forest activists’ motivations and their relational engagements with the forest. The aim is to explore what motivates the activist engagement, what enables and constrains it, how the activists’ personal relationship with the forest affects it as well as how the activist engagement affects this personal relationship. The theoretical framework is drawn from the concept of relational values in combination with posthumanist assemblage theory. The study is based on material gathered through semi-structured interviews with activists engaged in forest protection and through a participant observation conducted during a demonstration held for this cause. The study finds that a number of factors motivate the forest activism, the personal relationship with the forest being one important variable. The study further concludes that social relationships – both with fellow activists and with others – shape activist engagement in both positive and negative ways, and that these relations, alongside numerous other elements, constitute part of the activistship here analysed as an assemblage. Furthermore, the study finds that the interviewees' relationship with the forest has changed, and continues to do so, during the course of their activist engagement.