The post-traumatic osteolysis of the distal clavicle is very infrequent and the etiology and pathology is poorly understood. It is important to consider this possibility for differential diagnosis when continued pain in the acromio-clavicular joint (AC joint) follows blunt shoulder trauma. The course of the disease may result in a 3 cm loss of length of the distal clavicle. Months and years may pass until osteolysis becomes manifest, but the earliest radiological findings are present 4 weeks after trauma. The disease is self-limiting and usually does not leave residues. We report a case of a 35-year-old man with a post-traumatic osteolysis of the distal clavicle after blunt shoulder trauma. The diagnosis was determined several months after pain persisted in his shoulder. Using this case we discuss the possible pathogenic mechanism, differential diagnosis and treatment options for the post-traumatic osteolysis of the distal clavicle.