OBJECTIVE: Mindfulness-based cognitive therapy (MBCT) could be a treatment option for anxiety disorders. Although its effectiveness under conditions of low pharmacotherapy rates has been demonstrated, its effectiveness under condition of high pharmacotherapy rate is still unknown. The aim of the study was to evaluate effectiveness of MBCT under the context of high pharmacotherapy rates. RESULTS: A single arm with pre-post comparison design was adopted. Those who had any diagnosis of anxiety disorders, between the ages of 20 and 74, were included. Participants attended 8 weekly 2-hour-long sessions followed by 2 monthly boosters. Evaluation was conducted at baseline, in the middle, at end of the intervention, and at follow-up. The State-Trait Anxiety Inventory (STAI)-state was set as the primary outcome. Pre-post analyses with mixed-effect models repeated measures were conducted. Fourteen patients were involved. The mean age was 45.0, and 71.4% were female. The mean change in the STAI-state at every point showed statistically significant improvement. The STAI-trait also showed improvement at a high significance level from the very early stages. The participants showed significant improvement at least one point in some other secondary outcomes. Trial registration Retrospectively registered at the University Hospital Medical Information Network on 1st August 2013 (ID: UMIN000011347).