Background: Evidence-based guidelines recommend exercise-therapy as first line treatment for subacromial pain syndrome, but no previous study has mapped the content of care for subacromial pain syndrome and knowledge about adherence to clinical guidelines are lacking. We aim to describe the content and outcome of current care and investigate the relationship between content and outcome of care. Methods: We invited all patients diagnosed with subacromial pain syndrome at any Danish hospital to participate in this nationwide retrospective population-based cohort-study. Patient-reported information on content of care was collected using a validated questionnaire. Outcome of care was assessed using global impression of change (GIC) and patient acceptable symptom state (PASS). Invitations were sent 14 weeks after diagnosis. Results: In total, 3306 eligible patients participated. At follow-up, 45% had completed the recommended 12 weeks of exercise-therapy. From the total cohort, 12% underwent surgery without completing 12 weeks of exercise-therapy. For patients undergoing non-operative care, 43% reached PASS while 61% were improved since diagnosis at the hospital. Completing 12 weeks with exercise-therapy did not increase the odds of improvement (OR 1.05, 95%CI:0.88–1.24), but having conducted strengthening exercises did (OR 1.65, 95%CI:1.25–2.19). Conclusion: More than half of patients diagnosed with subacromial pain syndrome in specialist care settings do not adhere to recommendations regarding duration of exercise-therapy, but this is not related to symptom improvement. Conversely, conducting strengthening exercises relates to higher chance of symptom improvement. This challenges current clinical guidelines, indicating that a time-based cut-point may not be relevant while specific types of exercises are.