The purpose of this study was to determine the mortality rate and factors related to mortality in elderly patients with acute and monotraumatic femoral neck fractures. This study included 241 patients with femoral neck fractures after bipolar hemiarthroplasty. We analyzed the mortality rate and the relationship between postoperative mortality and risk factors, such as age, sex, body mass index, the time to surgery, and the Society of Anesthesiologists' score. The postoperative mortality rate 1 and 3 years after surgery was 11.2% and 19.5%, respectively. There proved to be a relationship between postoperative mortality and age, the time to surgery, and the Society of Anesthesiologists score. We recommend that surgery should not be delayed, and caution should be exercised for the high-risk group patients.