Posterior sternoclavicular (SC) dislocation is a rare diagnosis, which tends to be missed initially. Here we report two cases of a dislocated SC joint: one left and one right. The first case describes a 25-year-old male who sustained a direct injury caused by his seatbelt during a car accident. The diagnosis was made 3 months after the initial trauma following performance of a CT scan. His left SC joint was stabilized using a hamstring tendon allograft. The second patient, a 55-year-old female, sustained an indirect injury following a fall onto her right shoulder. The diagnosis was made 6 weeks after the trauma had occurred. Her SC joint was also stabilized using a tendon allograft reconstruction. The clinical outcome of both cases was very satisfactory. Better diagnostics - more attention for subtle symptoms during physical examination, the right choice of imaging (CT scan) and meticulous following of Advanced Trauma Life Support (ATLS) protocols - could diminish the number of delayed diagnoses in this rare but potentially dangerous injury.