INTRODUCTION: The treatment of closed humeral shaft fractures tends to be successful with functional bracing. Treatment failure due to iatrogenic conversion to an open fracture has not been described in the literature. We present a case series of patients that experienced open humeral shaft fractures after initially being treated with functional bracing for closed humeral shaft fractures and describe what factors are associated with this complication. MATERIALS AND METHODS: This was a retrospective case series performed at three level 1 trauma centers across North America. All nonoperatively treated humeral shaft fractures were reviewed from 2001 to 2023. Patients were included if they sustained a humeral shaft fracture, > 18 years old, were initially treated non-operatively with functional bracing which subsequently converted to an open fracture. Eight patients met inclusion criteria. All included patients were eventually treated with irrigation, debridement, and open reduction and internal fixation. Outcomes assessed included mortality rate, time until the fracture converted from closed to open, need for further surgery, and bony union. Descriptive statistics were used in analysis. RESULTS: The eight included patients on average were 65 ± 21.4 years old and had a body mass index (BMI) of 25.6 ± 5.2. Six patients were initially injured due to a fall. Time until the fractures became open on average was 5.2 ± 3.6 weeks. Three patients (37.5%) died within 1.8 ± 0.6 years after initial injury. The average Charlson Comorbidity Index (CCI) score was 4.5 ± 3.4. Three patients (37.5%) had dementia. Common characteristics among this cohort included a history of visual disturbances (50.0%), cerebrovascular accident (50.0%), smoking (50.0%), and alcohol abuse (50.0%). CONCLUSION: Conversion from a closed to open humeral shaft fracture after functional bracing is a potentially devastating complication. Physicians should be especially cognizant of patients with a low BMI, history of falling or visual disturbance, dementia, age  ≥  65, decreased sensorimotor protection, and significant smoking or alcohol history when choosing to use functional bracing as the final treatment modality. LEVEL OF EVIDENCE: IV.