AIMS AND OBJECTIVES: To investigate the effectiveness and acceptability, and thus practicability of a biopsychosocial-based exercise model in rheumatic diseases by a mixed method. METHOD: This study is within the framework of mixed-method research that combines the strengths of quantitative and qualitative research methodologies. For the quantitative part of the study, 81 patients were divided into two groups Bilişsel Egzersiz Terapi Yaklaşımı (BETY)- (Cognitive Exercise Therapy Approach in English) exercise group (BETY Group-BG) and control group (CG). BG participants engaged in supervised exercise sessions with a physiotherapist for 1 h, three times weekly, over 12-week periods, while CG participants continued only routine medical treatment. Biopsychosocial status (BETY-Biopsychosocial Questionnaire [BETY-BQ]), functionality (Health Assessment Questionnaire [HAQ]), emotional status (Hospital Anxiety and Depression Scale [HADS]), and quality-of-life (Short Form-36 [SF-36]) was evaluated at baseline and 12 weeks. Qualitative data was collected from 20 patients who have acquired the habit of regular exercise by attending the BETY group exercise programme. Individual, semi-structured, face-to-face interviews were recorded, transcribed, and condensed and interpreted based on pre-established themes. RESULT: There were differences in the BETY-BQ, HAQ, HADS-D, and SF-36 scores between baseline and 12 weeks in the BG (p <
0.05). Additionally, in post-intervention, the BETY-BQ, HADS-A, and SF-36 scores differences between groups were in favour of the BG (p <
0.05). In qualitative analysis, four sections were investigated, which were subdivided into 'Biopsychosocial Status', 'Functionality', 'Emotional Status' and 'Quality of Life'. CONCLUSION: BETY is an effective and acceptable exercise model for managing the symptoms of patients with rheumatic diseases.