OBJECTIVES: To explore possible working mechanisms of anxiety reduction in women with anxiety disorders, treated with art therapy (AT). METHODS: A RCT comparing AT versus waiting list (WL) condition on aspects of self-regulation. Stress regulation (heart rate and heart rate variability) and executive functioning (daily behavioural and cognitive performance aspects of executive functioning (EF)) were evaluated in a pre-post design. Participants were women, aged 18-65 years with moderate to severe anxiety symptoms. RESULTS: Effectiveness of AT compared to WL was demonstrated in a higher resting HRV post treatment, improvements in aspects of self-reported daily EF (emotion control, working memory, plan/organize and task monitor), but not in cognitive performance of EF, stress responsiveness and down regulation of stress. The decrease in anxiety level was associated with improvements in self-reported daily EF. CONCLUSIONS: AT improves resting HRV and aspects of EF, the latter was associated with art therapy-related anxiety reduction.