Nature-based therapy can be considered an umbrella term for a diverse range of psychotherapeutic and allied practices which integrate experiences and activities in nature as therapeutic means. The objective of this article is to describe the theoretical framework for nature-based therapy in a university-founded healing forest garden near Copenhagen, Denmark. The garden will offer a 10-week treatment for people who are on sick leave with stress-related illness. This article focuses on clarifying the integration between the psychotherapeutic and gardening aspects of the nature-based therapy. The psychotherapeutic aspects are based on mindfulness and an acceptance therapy, while the gardening aspects are highly inspired by permacultural principles and methods.