Acromioclavicular (AC) dislocation is a common type of shoulder injury. Although the incidence of acromioclavicular dislocation is frequent, there are different opinions regarding the treatment. Many different techniques have been proposed for the surgical treatment of AC dislocations, but all these methods have been questioned from different angles, and the gold standard in terms of treatment has not yet been determined. There are six types described by Rockwood et al. and type 6 has two types: subacromial and subcoracoid. Subcoracoid AC Type 6 dislocations are seen very rarely and difficult to diagnose in initial clinical findings or can be simply overlooked due to associated more serious injuries which take more attention. The mechanism of injury of a type 6 AC dislocation is hyperabduction and external rotation of the shoulder. A small number of type 6 subcoracoid AC dislocations have formerly been reported and apart from one case all of them were acutely diagnosed and treated with open reduction and internal fixation. In this paper, we report a case of late diagnosis of subcoracoid type 6 AC dislocation, along with its rare and previously unreported surgical management.