This paper evaluates the impact of the forest environment on aggressive manifestations in adolescents. A remedial educative programme was performed with 68 teenagers from institutions with substitute social care with diagnoses F 30.0 (affective disorders) and F 91.0 (family-related behavioural disorders), aged 12–16 years. Adolescents observed patterns of prosocial behaviour in forest animals (wolves, wild boars, deer, bees, ants, squirrels and birds), based on the fact that processes and interactions in nature are analogous to proceedings and bonds in human society. The methodology is based on qualitative and quantitative research. Projective tests (Rorschach Test, Hand Test, Thematic Apperception Test) were used as a diagnostic tool for aggressive manifestations before and after forest therapies based on Shinrin-yoku, wilderness therapy, observational learning and forest pedagogy. Probands underwent 16 therapies lasting for two hours each. The experimental intervention has a statistically significant effect on the decreased final values relating to psychopathology, irritability, restlessness, emotional instability, egocentrism, relativity, and negativism. Forest animals demonstrated to these adolescents ways of communication, cooperation, adaptability, and care for others, i.e., characteristics without which no community can work.