There is controversy about the therapy for third-degree acromioclavicular dislocation according to Tossy and Rockwood's classification. Both operative and non-operative treatment is reported to have satisfactory results in the literature. The purpose of this study was to analyze the literature in a systematic manner based on the criteria of evidence-based medicine. It was our hypothesis that there is no scientific evidence for the superiority of one treatment over the other. A total of 370 papers were retrieved and classified into three groups: (1) randomized controlled trials; (2) comparative retrospective studies; and (3) retrospective studies. In three studies that were graded with high evidence, the major outcome for both operative and non-operative treatment was similar. The advantages of non-operative treatment include a shorter period of rehabilitation and a significantly lower complication rate while the advantages of operative treatment include a low rate of persisting subluxation of the AC joint. Similar results were found for retrospective comparative and long-term studies. For retrospective studies without controls, both operative and conservative therapy are described with good and excellent results, ranging between 80 and 97%. In conclusion, there is good evidence on the therapy of third-degree acromioclaviculary dislocation studies. The functional result according to the literature is similar, and complications associated with therapy occur more often with operative treatment. Conservative treatment appears to be the method of choice for third-degree acromioclavicular dislocations unless the patient's preference is operative therapy.