Aims. Our aim was to investigate the outcomes of patients with a displaced fracture of the glenoid fossa who are treated conservatively. There is little information in the literature about the treatment of these rare injuries non-operatively. Patients and Methods. We reviewed 24 patients with a mean age of 52 years (19 to 81) at a mean of 5.6 years (11 months to 18 years) after the injury. Results. At final follow-up, the mean Constant and Murley score was 79 points (18 to 98); the mean Western Ontario Shoulder Instability Index score (WOSI) was 77% (12 to 100) and the mean Rowe score was 93 points (50 to 100). Fractures with little intra-articular displacement (≤ 3 mm) had an uneventful outcome. Those with intra-articular displacement of ≤ 3 mm had a significant better mean Constant and Murley score than those with displacement of ≥ 5 mm and/or a fracture gap of ≥ 5 mm. Poor clinical results such as nonunion and post-traumatic osteoarthritis were associated with displaced or angulated glenoid fragments and significant intra-articular displacement. Conclusion. Glenoid fossa fractures with displacement of ≥ 5 mm should be treated surgically if the patient’s condition allows. Displacement and angulation can lead to nonunion and a poor outcome if the degree of displacement results in a persistent fracture gap in the glenoid fossa or if the angulation of fragments leads to malunion. Cite this article: Bone Joint J 2016;98-B:1074–9