Purpose: To evaluate the efficacy of the preventive abduction brace in dementia patients after bipolar hemiarthroplasty of the hip. Materials and Method: A review of 30 patients who had dementia prior to bipolar hemiarthroplasty of the hip. 20 females and 10 males were evaluated and their mean age was 80.4 years old (range, 68 to -92 years old). The average MMSE-K in dementia patients was 14.2 (range, 8 to 20). The reasons for the bipolar hemiarthroplasties were femoral neck fractures in all the cases. We analyzed the dislocation rates of those who had preventive abduction braces applied prospectively. Results: The average follow-up period after hemiarthroplasty was 2.2 years. All 30 patients had preventive abduction braces and no dislocations occurred after the bipolar hemiarthroplasties. Conclusion: Hip dislocations were not detected in those patients who preventive abduction braces applied. The present findings suggest that having a preventive abduction brace will definitely reduce the dislocation rate in dementia patients who have difficulties with rehabilitation after their operations.