Radically Open Dialectical Behaviour Therapy (RO DBT) is a new treatment for overcontrolled mental health disorders, including refractory depression. This case study provides the therapist’s description of delivering RO DBT to a client who took part in a randomised controlled trial of RO DBT. It describes novel treatment strategies and their implementation. Sam attended weekly individual sessions and group skills training sessions over 7 months. The treatment involved collaboratively explaining the RO DBT model whilst linking it to Sam’s history and experiences. Coping styles that served to keep Sam isolated from others were identified with a focus on social signalling. RO DBT skills were introduced to activate her social safety system and enhance connectedness. Percentage improvement in depression scores from baseline was 50% at 7 months (end of treatment) and 65% at 18 months.Sam was in full remission at 12 and 18 months. Subjective feedback from Sam was that she felt happier in her marriage, had started voluntary work and made friends locally. She reported being more compassionate to herself and having increased flexibility in adapting to situations.The therapist reported using the RO DBT skills herself and finding them useful, both in learning the new therapy and in the therapy sessions. RO DBT’s focus on the overcontrolled coping style and teaching of new strategies to address social signalling and enhance connectedness is a novel treatment approach. It offers promise as an intervention for those with depression.