Background: There is a lack of research on psychological treatments for psychosis in the inpatient setting. Acceptance and Commitment Therapy for psychosis (ACTp) is a diagnose specific adaptation of the transdiagnostic ACT treatment model which has shown promising results in patients with psychosis. Aim: The aim was to explore treatment effects of ACTp on inpatients with psychosis on symptoms, level of functioning, level of activity, psychological flexibility, -health-related quality of life, valued living, and to explore the acceptability and feasibility of ACTp. Method: Twelve inpatients with psychosis were treated with 3-10 daily sessions of ACTp in a non-concurrent single case AB design with additional pre-post and mid-measures. The mean age at clinic A was 48.88 (SD = 11.59) and 48.75 (SD = 16.07) at clinic B. We calculated non - overlap of all pairs (NAP) in daily measures, and reliable change index (RCI), and clinical significance in pre-post measures. Results: Half of the participants improved significantly on health-related quality of life and depression in daily measures and on depression and anxiety in pre-post measures. ACTp was quite acceptable and recruitment and the deliverance of therapy in the inpatient setting was feasible. Conclusion: In the present study, participants found the ACTp treatment to be comprehensive and helpful. Recruitment and treatment of inpatients were feasible, however, since most participants were discharged before ACTp protocol was completed, fewer sessions or having sessions more frequently needs further investigation. Daily measurement showed a significant improvement in health-related quality of life and depression for a majority of the participants.