Recent demographic changes in the forest-owner structure are suspected to have led to the increasing number of owners with no specific objectives for their forests. In addition, the continuous fragmentation of the forest holdings has increased the threat of the passiveness related to forest management. To decrease the tendency towards passiveness, new policy tools and initiatives have been suggested. In the Finnish context, the idea of an investor-based jointly owned forest has been introduced as facilitating the effective utilization of the forest resource. However, collective ownership has faced prejudice and scepticism among private forest owners. In order to expand, the forest owners need to see the idea of jointly owned forests as a socially legitimate. Thus, by adopting Van Leeuwen's framework for analyzing the legitimation of new social practices, we examine how Finnish forest owners legitimate their participation in jointly owned forests. The qualitative data of the study consist of 20 in-depth interviews with private forest owners who have joined a jointly owned forest. Our study contributes to the recent discussion on jointly owned forests. We show how a change in the type of ownership results in moral, authoritative and rational justifications over the decision while simultaneously renewing the identity of the forest owner. Accordingly, we suggest that forest ownership is not only driven by rational prospects, but the moral and emotional nature of ownership should be better taken into account at the policy level and in structural designs when discussing the promotion of new types of forest ownership.