Background/aim: The Tree Theme Method (TTM) is an intervention in which the client paints trees representing certain periods in his/her life. The intervention comprises five sessions, using trees as a starting point to tell one's life story. This study, which is part of an implementation project, aimed to examine the therapeutic alliance and client satisfaction, in relation to perceptions of everyday occupations and health-related factors, with clients going through a TTM intervention. Methods: Nine occupational therapists recruited 35 clients, at general outpatient mental health care units, for the TTM intervention. Self-rating instruments, targeting therapeutic alliance (HAq-II), different aspects of daily occupations (Canadian Occupational Performance Measure, Satisfaction with Daily Occupations), health-related factors (Sense of Coherence measure, Mastery Scale, Symptom Checklist-90-R) and client satisfaction (Client Satisfaction Questionnaire), were administrated before and after the intervention. Results: A good initial therapeutic alliance, experienced by both therapists and clients, was correlated to increased changes regarding occupational performance and self-mastery. According to the therapists' ratings, a good initial therapeutic alliance was correlated to increased sense of coherence and a decreased level of psychiatric symptoms. The results showed positive significant changes in occupational performance and health-related factors. High ratings of the therapeutic alliance by the therapists were also related to high client satisfaction. Conclusions: The TTM seemed to function well in psychosocial occupational therapy, but there is a need for further implementation studies to deepen our understanding of the treatment process, comprising both technique and formation of the therapeutic alliance.